Curative Treatment on Hyperglycemia in Cushing Syndrome

A retrospective analysis of data from more than 170 patients with Cushing syndrome and hyperglycemia provides insight into the effects of curative treatment on hyperglycemia among these patients.

An analysis of retrospective data from a 20-year period details the impact of curative treatment on hyperglycemia among patients with Cushing syndrome.

Led by a team of investigators from the Mayo Clinic in Rochester, MN, the study examined a cohort of 174 adult patients with Cushing Syndrome and determined 2-in-3 patients with hyperglycemia experienced resolution or improvement of hyperglycemia after a curative procedure.

“This is the first study to analyze the quantitative changes based on the time from the curative surgery, to assess the changes in the intensity of hyperglycemia therapy and identify predictors for hyperglycemia improvement,” wrote investigators.

A team led by Irina Bancos, MD, endocrinologist at the Mayo Clinic Rochester, designed the current study with an interest in examining the impact of curative procedures on hyperglycemia and its management in patients with Cushing syndrome from electronic medical record data of patients treated at a referral center from 2000-2019. The primary purpose of the study was to assess the impact of curative procedures on extent of hyperglycemia and the secondary aim was to investigators how baseline factors might influence improvement of hyperglycemia at follow-up.

For inclusion in the analysis, patients needed to be at least 18 years of age, diagnosed with Cushing syndrome, and have hyperglycemia treated with a curative procedure from January 1, 2000-November 1, 2019. For the purpose of analysis, Cushing syndrome was diagnosed based on clinical evaluation by an endocrinologist and diagnosed according to the most recent guidelines. Hyperglycemia was defined according to American Diabetes Association guidelines.

The primary outcome of interest for the study was the resolution of hyperglycemia following resolution of Cushing syndrome. For the purpose of analysis, resolution was defined as absence of hyperglycemia without the need for antihyperglycemic therapy. Secondary outcomes of interest included changes in HbA1c, and the intensity of hyperglycemia management.

Overall, 174 patients were identified for inclusion in the study. This cohort had a median age of diagnosis of 51 (range, 16-82) years and 73% (n=127) were women. When assessing subtype of Cushing syndrome, the most common form was pituitary Cushing syndrome (60.9%), followed by ectopic (14.4%), and adrenal (24.7%). The median baseline HbA1c was 6.9% (range, 4.9-13.1), 24% of patients were not on any therapy for hyperglycemia, 52% were on oral medications, and 37% were on insulin (mean daily units, 58; range, 10-360).

When assessing differences between subtypes, results indicated those with pituitary Cushing syndrome were younger at the time of surgery (P=.0009), and included more women (P=.0023), and reported a longer duration of symptoms prior to diagnosis. Investigators noted patients with pituitary Cushing syndrome also had the highest clinical severity score (<.0001), but patients with ectopic Cushing syndrome had the highest biochemical severity score (P <.0001).

Following Cushing syndrome remission and at the end of follow-up, which occurred at a median of 10.5 months, 21% of patients demonstrated resolution of hyperglycemia, 47% demonstrated improvement, and 32% had no change or worsening hyperglycemia. When assessing secondary end points, results indicate HbA1c decreased by 0.84% (P <.0001) and daily insulin dose decreased by a mean of 30 units (P <.0001). Further analysis indicated hypercortisolism severity score (severe vs moderate/mild: OR, 2.4; 95% CI, 1.1-4.9) and Cushing syndrome subtype (nonadrenal vs adrenal: OR, 2.9; 95% CI, 1.3-6.4) were associated with hyperglycemia improvement, but not type of hyperglycemia (diabetes vs prediabetes: OR, 2,1; 95% CI, 0.9-4.9) at the end of follow-up.

“We demonstrated that almost 70% of patients with CS demonstrate either resolution or improvement in hyperglycemia following CS remission. As a group, patients demonstrate a decrease in HbA1c, and can be treated with less insulin and fewer non-insulin agents. Patients with more severe hyperglycemia, ACTH-dependent CS, and more severe CS are more likely to improve after surgery,” added investigators.

This study, “The impact of curative treatment on hyperglycemia in patients with Cushing syndrome,” was published in The Journal of the Endocrine Society.

From https://www.endocrinologynetwork.com/view/obesity-overweight-responsible-for-1-in-5-future-thyroid-cancers-in-australia

Pituitary MRI standard and advanced sequences: Role in the diagnosis and characterization of pituitary adenomas

This article involves discussion on the use of standard and advanced magnetic resonance imaging (MRI) sequences to diagnose and characterize pituitary adenomas (PAs), including MRI characteristics related to treatment response that could assist in presurgical assessment and planning, and red flags that could suggest an alternative diagnosis.

  • Besides PAs, several other lesions may be found in the sellar region, such as meningiomas, craniopharyngiomas and aneurysms.
  • For assessing lesions in the sella turcica, sellar MRI is preferred.
  • With a systematic MRI approach to the pituitary region, generally the obtained information comprises: the size and shape of the PA, the presence of cysts or hemorrhage within the tumor, its link with the optic pathways and surrounding structures, potential cavernous sinus invasion, sphenoid sinus pneumatization type, and differential diagnosis with other sellar lesions.
  • In the majority of cases, standard protocol serves the purpose; but additional information could be obtained by using some advanced techniques (susceptibility imaging, diffusion-weighted imaging, 3D T2-weighted high-resolution sequences, magnetic resonance elastography, perfusion-weighted imaging) and such information may be important for some cases.

Adrenal: How the SARS-CoV-2 virus undermines our body’s ‘fight’ response

Researchers in Europe say they have shown for the first time that the SARS-CoV-2 virus attacks the human stress system by limiting how our adrenal glands can respond to the threat of Covid-19.

According to a study, the coronavirus targets the adrenal glands, thereby weakening the body’s ability to produce the stress hormones cortisol and adrenaline needed to help battle a serious infection.

Part of the body’s defence mechanism, these glands are indispensable for our survival of stressful situations, particularly with a coronavirus infection.

The research was published by a group of scientists in London, United Kingdom; Zurich, Switzerland; and Dresden and Regensburg in Germany, in the journal The Lancet Diabetes and Endocrinology last month (November 2021).

“The results of our latest work now show for the first time that the virus directly affects the human stress system to a relevant extent,” says Dr Stefan Bornstein, director of the Medical Clinic and Polyclinic III and the Centre for Internal Medicine at the University Hospital in Dresden.

Whether these changes directly contribute to adrenal insufficiency, or even lead to long Covid is still unclear, he says.

This question must be investigated in further clinical studies.

Pointing to recent research showing the effect of inhaling steroids to prevent clinical deterioration in patients with Covid-19, the researchers say certain drugs may be able to help limit this effect of the SARS-CoV-2 virus.

“This evidence underlines the potentially important role for adrenal steroids in coping with Covid-19,” scientists at the University of Zurich say.

The researchers analysed the data of 40 deceased Covid-19 patients in Dresden and found that their tissue samples showed clear signs of adrenal gland inflammation.

From https://www.thestar.com.my/lifestyle/health/2021/12/22/how-the-sars-cov-2-virus-undermines-our-bodys-039fight039-response

Topical Corticosteroid-Induced Iatrogenic Cushing Syndrome in an Infant

https://doi.org/10.1016/j.amsu.2021.102978Get rights and content
Under a Creative Commons license

Highlights

Cushing syndrome is an abnormality resulting from high level of blood glucocorticoids.

Iatrogenic Cushing syndrome due to the overuse of topical corticosteroids is rarely reported.

This report presents a case of topical corticosteroid induced iatrogenic Cushing syndrome in an infant.

Abstract

Introduction

Cushing syndrome (CS) is an endocrinological abnormality that results from a high level of glucocorticoids in the blood. Iatrogenic CS due to the overuse of topical corticosteroids is rarely reported. The current study aims to present a rare case of topical corticosteroid induced iatrogenic CS in an infant.

Case presentation

A 4-month-old female infant presented with an insidious onset of face puffiness that progressed over a 2-month period. The mother reported to have used a cream containing Betamethasone corticosteroid 5–8 times a day for a duration of 3 months to treat diaper dermatitis. Laboratory findings revealed low levels of adrenocorticotrophic hormone (ACTH) and serum. Abdominal ultrasound showed normal adrenal glands. The topical corticosteroid was halted and physiologic topical hydrocortisone doses were administered.

Clinical discussion

Infants are more likely to acquire topical corticosteroid induced iatrogenic CS due to their thin and absorptive skin, higher body surface area, and the high prevalence of conditions that necessitates the use of these medications. Most iatrogenic CS cases following topical steroid application have been reported in infants with diaper dermatitis that are most commonly treated with Clobetasol and Bethamethasone.

Conclusion

Infants are susceptible to develop CS due to topical corticosteroid overuse. Hence, physicians need to consider this in infantile CS cases, and take appropriate measures to avoid their occurrence.

Keywords

Cushing syndrome
Infant
Iatrogenic
Topical corticosteroid

1. Introduction

Cushing syndrome (CS) is a reversible endocrinological abnormality that results from high level of cortisol or other glucocorticoids in the blood [1]. It can be caused by either endogenous factors such as excess steroid production and secretion due to adrenal or pituitary tumors, or exogenously through prolonged use of corticosteroid medications resulting in iatrogenic CS [2]. Iatrogenic CS due to the overuse of oral or parenteral corticosteroids is common, however, while topical corticosteroids are one of the most widely prescribed medications by dermatologists, they are less frequently reported to cause iatrogenic CS [3,4]. Even though CS is very rare in the pediatric population with an annual incidence of only 5 cases per million, children of the pediatric age have a higher risk of developing iatrogenic CS, which is likely due to the high prevalence of conditions that necessitates the use of topical corticosteroids and the thinness of their skin that can more easily absorb the steroid [5,6].

The aim of the current study is to present a rare case of topical corticosteroid induced iatrogenic CS in an infant. SCARE guidelines are considered in writing this report [7].

2. Case presentation

2.1. Patient information

A 4-month-old female infant presented with an insidious onset of puffiness of the face; the swelling progressed over a period of 2 months without any other associated symptoms. The infant’s prenatal, developmental, and family history were insignificant, and she was born full term to consanguineous parents via caesarian delivery. After delivery she did not require neonatal intense care unit (NICU) and was discharged in good health. She has been given both bottle and breastfeeding every one to two hrs, and she has received all the required vaccinations at their proper times.

The mother reported to have used a topical corticosteroid cream (Optizol-B cream; a combination of Clotrimazole and Betamethasone) for a period of 3 months with a dose of 5–8 times a day to treat diaper dermatitis of the infant.

2.2. Clinical findings

The infant’s physical examination revealed facial puffiness (Moon face) with no body edema, and cutaneous examination showed the diaper rash without any other cutaneous manifestations. The infant was vitally stable with no dysmorphic features and no skeletal deformities. Her growth parameters were within normal limits, and her systemic examination was unremarkable.

2.3. Diagnostic approach

Laboratory findings revealed low adrenocorticotropic hormone (ACTH) level in the blood measuring 5.9 p.m./l, a serum cortisol level of 24 nmol/l, and normal serum sodium and potassium levels of 144 mEq/l and 4.8 mmol/l, respectively. Abdominal ultrasonography (US) showed normal adrenal glands.

2.4. Therapeutic intervention

The topical corticosteroid cream that contained Bethamethasone was halted and oral hydrocortisone was given (10 mg/m2) tapered over one month. The patient was given a card addressing Cushing syndrome to inform the health care providers in case of emergency situation or unexpected surgical intervention.

2.5. Follow-up and outcome

The infant’s facial puffiness was significantly improved after 7-month follow-up of the patient.

3. Discussion

CS is an endocrinological disorder resulting from high glucocorticoid level in the blood, it is categorized into ACTH dependent (due to pituitary tumors or excess ACTH administration) or ACTH independent CS (due to adrenal neoplasms or excessive glucocorticoid intake) [8,9]. Under normal circumstances, ACTH is secreted by the pituitary gland which in turn stimulates the secretion of cortisol by the adrenal glands [10]. Prolonged exogenous corticosteroid administration can lead to a number of adverse effects based on potency and duration of the treatment, including the suppression of hypothalamic-pituitary-adrenal (HPA) axis and iatrogenic CS, severe infections, and failure to thrive [11]. While iatrogenic CS is frequent with prolonged administration of oral or parenteral corticosteroids, it is occurrence due to topical corticosteroids have rarely been reported [12].

Multiple factors can increase the probability of acquiring the condition, such as corticosteroid potency, amount and frequency of application, age, skin quality, presence of occlusion, and duration of application [4]. In general, infants are more likely to develop topical corticosteroid induced iatrogenic CS, this is due to their thin and absorptive skin, higher body surface area, underdeveloped skin barrier, and the high prevalence of conditions that necessitates the use of these medications [5,6]. Most iatrogenic CS cases following topical steroid application have been reported in infants with diaper dermatitis [8]. This was also the case in this study. This is likely because the diaper area provides occlusion, the perineal skin has intrinsically absorptive properties, the steroid causes local skin atrophy, and percutaneous absorption is even more increased as the result of skin inflammation [13].

The most frequently used corticosteroid for the treatment of diaper dermatitis is reported to be Clobetasol followed by Bethamethasone, with a mean application duration of 2.75 (1–17) months to induce cortisol and ACTH levels suppression [4]. Typical clinical manifestations of CS include facial puffiness (Moon face), generalized body edema and obesity, hirsutism, buffalo hump, hypertension, skin fragility, and purple striae [3,5]. The causative corticosteroid in the current case was Bethamethasone that only resulted in facial puffiness (Moon face) without generalized body edema.

A specific and definitive diagnostic approach for iatrogenic CS is currently lacking [5]. However, prolonged exogenously administered glucocorticoids can suppress ACTH secretion which results in dismissing the need for proper endogenous production of cortisol [14]. Hence, almost all iatrogenic CS cases are associated with low ACTH and cortisol levels which can aid in the diagnosis of the condition [8]. Same findings were observed in this case. According to multiple studies, exogenous corticosteroid administration can often lead to HPA axis suppression alongside CS [15,16]. However, topical corticosteroid induced iatrogenic CS has been reported without HPA axis suppression [8].

The management of these cases start with the cessation of the causative corticosteroid medication and administration of physiologic topical hydrocortisone [5]. The same approach was followed in this study. In order to prevent the development of this condition in the first-place; clinicians should avoid prescribing high potency corticosteroids in the treatment of infantile dermatological disorders and instead choose low potency topical steroids, and also parents should be advised not to overuse these medications and only apply a thin layer to the affected area [6].

In conclusion, even though iatrogenic CS in infants is rare, overuse of topical corticosteroids can lead to their occurrence. Hence, physicians need to consider extensive steroid use as a causative agent of infantile CS. Appropriate measures need to be taken to avoid their occurrence by prescribing less potent steroids, limiting the use of high potent steroids, and informing parents about adverse effects of steroid overuse in infants.

Source of funding

None is found.

Author statement

Soran Mohammed Ahmed: physician managing the case, follow up the patient, and final approval of the manuscript.

Shaho F. Ahmed, Snur Othman, Berwn A. Abdulla, Shvan M.Hussein, Abdulwahid M.Salih, and Fahmi H. Kakamad: literature review, writing the manuscript, final approval of the manuscript.

Patient consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Provenance and peer review

Not commissioned, externally peer-reviewed.

Guarantor

Fahmi Hussein Kakamad.

Declaration of competing interest

None to be declared.

References

© 2021 The Authors. Published by Elsevier Ltd on behalf of IJS Publishing Group Ltd.

Assessment of Vitamin D Metabolism in Patients with Cushing’s Disease

Endocrinology Research Centre, 117292 Moscow, Russia
*
Author to whom correspondence should be addressed.
Academic Editor: Spyridon N. Karras
Nutrients 202113(12), 4329; https://doi.org/10.3390/nu13124329
Received: 12 November 2021 / Revised: 26 November 2021 / Accepted: 27 November 2021 / Published: 30 November 2021

Abstract

In this study we aimed to assess vitamin D metabolism in patients with Cushing’s disease (CD) compared to healthy individuals in the setting of bolus cholecalciferol treatment. The study group included 30 adults with active CD and the control group included 30 apparently healthy adults with similar age, sex and BMI. All participants received a single dose (150,000 IU) of cholecalciferol aqueous solution orally. Laboratory assessments including serum vitamin D metabolites (25(OH)D3, 25(OH)D2, 1,25(OH)2D3, 3-epi-25(OH)D3 and 24,25(OH)2D3), free 25(OH)D, vitamin D-binding protein (DBP) and parathyroid hormone (PTH) as well as serum and urine biochemical parameters were performed before the intake and on Days 1, 3 and 7 after the administration. All data were analyzed with non-parametric statistics. Patients with CD had similar to healthy controls 25(OH)D3 levels (p > 0.05) and higher 25(OH)D3/24,25(OH)2D3 ratios (p < 0.05) throughout the study. They also had lower baseline free 25(OH)D levels (p < 0.05) despite similar DBP levels (p > 0.05) and lower albumin levels (p < 0.05); 24-h urinary free cortisol showed significant correlation with baseline 25(OH)D3/24,25(OH)2D3 ratio (r = 0.36, p < 0.05). The increase in 25(OH)D3 after cholecalciferol intake was similar in obese and non-obese states and lacked correlation with BMI (p > 0.05) among patients with CD, as opposed to the control group. Overall, patients with CD have a consistently higher 25(OH)D3/24,25(OH)2D3 ratio, which is indicative of a decrease in 24-hydroxylase activity. This altered activity of the principal vitamin D catabolism might influence the effectiveness of cholecalciferol treatment. The observed difference in baseline free 25(OH)D levels is not entirely clear and requires further study.

1. Introduction

Cushing’s disease (CD) is one of the disorders associated with endogenous hypercortisolism and is caused by adrenocorticotropic hormone (ACTH) hyperproduction originating from pituitary adenoma [1]. Skeletal fragility is a frequent complication of endogenous hypercortisolism, and fragility fractures may be the presenting clinical feature of disease. The prevalence of osteoporosis in endogenous hypercortisolism as assessed by dual-energy X-ray absorptiometry (DXA) or incidence of fragility fractures has been reported to be up to 50%. Osteoporosis in CD patients has a complex multifactorial pathogenesis, characterized by a low bone turnover and severe suppression of bone formation [2]. Exogenous glucocorticoids are used in the treatment of a wide range of diseases and it is estimated that 1–2% of the population is receiving long-term glucocorticoid therapy. As a consequence, glucocorticoid-induced osteoporosis is the most common secondary cause of osteoporosis [3].
Native vitamin D (in particular D3, or cholecalciferol) and its active metabolites (such as alfacalcidol) are universally considered as the essential components of the osteoporosis management [4,5]. The search for the optimal treatment of bone complications during chronic exposure to glucocorticoid excess provoked the investigation of vitamin D metabolism in this state. Early studies on this topic were focused predominantly on the general vitamin D status (assessed as 25(OH)D level) and on the levels of the active vitamin D metabolite (1,25(OH)2D). These studies showed inconsistent results, reporting that the chronic excess of glucocorticoids decreased [6,7,8,9], increased [10,11,12] or did not change [13,14,15] the levels of 25(OH)D or 1,25(OH)2D. A likely reason for such inconsistency might have been the high heterogeneity of the studied groups. Some of these studies were performed in humans [6,7,9,10,11,12,13,15] and some in animal models [8,14], and only several of them included subjects with specifically endogenous hypercortisolism [10,12,14,15]. Only two studies assessed both the levels of the active (1,25(OH)2D) and the inactive (24,25(OH)2D) vitamin D metabolites in endogenous hypercortisolism. One of them lacked control group and reported low-normal 24,25(OH)2D levels in patients with Cushing’s syndrome [10]. The second study by Corbee et al. reported similar circulating concentrations of 25(OH)D, 1,25(OH)2D and 24,25(OH)2D in studied groups of dogs regardless of either the presence of CD or hypophysectomy status [14].
Several experimental studies were performed to evaluate the impact of glucocorticoid excess on the enzymes involved in vitamin D metabolism. In mouse kidney glucocorticoid treatment increased 24-hydroxylase expression [16] and 24-hydroxylase activity [17]. An increased expression of 24-hydroxylase was also shown in rat osteoblastic and pig renal cell cultures treated with 1,25(OH)2D [18]. Dhawan and Christakos showed that 1,25(OH)2D-induced transcription of 24-hydroxylase was glucocorticoid receptor-dependent [19]. However, some works showed conflicting results. In particular, the steroid and xenobiotic receptor (SXR) which is activated by glucocorticoids [20], repressed 24-hydroxylase expression in human liver and intestine in work by Zhou et al. [21]. Lower 24-hydroxylase expression was observed in the brain and myocardium of glucocorticoid-treated rats [22] as well as in human osteosarcoma cells and human osteoblasts [23].
Nevertheless, based on experimental data, it has been suggested that the acceleration of 25(OH)D catabolism in the presence of glucocorticoid excess may predispose to vitamin D deficiency. Yet, relatively recent meta-analysis of the studies assessing 25(OH)D levels in chronic glucocorticoid users showed that serum 25(OH)D levels in these patients were suboptimal and lower than in healthy controls, but similar to steroid-naive disease controls [24].
Glucocorticoids also affect calcium and phosphorus homeostasis. In particular, they were shown to reduce gastrointestinal absorption by antagonizing vitamin D action (reducing the expression of genes for proteins involved in calcium transport—epithelial Ca channel TRPV6 and calcium-binding protein calbindin-D9K) [25]. Glucocorticoids increased fractional calcium excretion due to mineralocorticoid receptor-mediated action on epithelial sodium channels [26]. Hypercalciuria is highly prevalent in people with CD [27]. These effects might result in a negative calcium balance, although plasma ionized calcium was normal in people and dogs with hypercortisolism compared to control subjects [12,28]. Glucocorticoids also reduced tubular phosphate reabsorption by inhibiting tubular expression of the sodium gradient-dependent phosphate transporter, and induced phosphaturia [29], which was accompanied by phosphate lowering in humans [12].
Overall, current data on vitamin D status in hypercortisolism are conflicting and need clarification. In particular, clinical data on the state of vitamin D metabolism in the state of glucocorticoids excess are quite scarce. Studies were very heterogeneous in design, some lacked a control group, and the absolute majority of the studies were performed before the introduction of vitamin D measurement standardization [30]. Nevertheless, determining the optimal vitamin D treatment regimen in these high-risk patients is fairly relevant.
The aim of this study was to assess vitamin D metabolism in patients with CD compared to healthy individuals particularly in the setting of cholecalciferol treatment.

2. Materials and Methods

2.1. Study Population and Design

The study group included 30 adult patients with CD admitted for inpatient treatment at a tertiary pituitary center. Diagnosis of CD was established in accordance with the federal guidelines [31]. All patients were confirmed to be positive for endogenous hypercortisolism in at least two of the following tests: 24-h urine free cortisol (UFC) greater than the normal range for the assay and/or serum cortisol > 50 nmol/L after the 1-mg overnight dexamethasone suppression test and/or late-night salivary cortisol greater than 9.4 nmol/L). All patients also had morning ACTH ≥ 10 pg/mL and pituitary adenoma ≥ 6 mm identified by magnetic resonance imaging (MRI) or a positive for CD bilateral inferior petrosal sinus sampling (BIPSS). MRI was performed using a GE Optima MR450w 1.5T with Gadolinium (Boston, MA, USA). BIPSS was performed according to the standard procedure described elsewhere [32,33].
The control group included 30 apparently healthy adult individuals recruited from the staff and the faculty of the facility.
Inclusion criteria were age from 18 to 60 for both groups and the presence of the disease activity for the study group (defined as the presence of endogenous hypercortisolism at the time of participation in the study). Exclusion criteria for both groups were: vitamin D supplementation for 3 months prior to the study; severe obesity (body mass index (BMI) ≥ 35 kg/m2); pregnancy; the presence of granulomatous disease, malabsorption syndrome, liver failure; decreased GFR (less than 60 mL/min per 1.73 m2); severe hypercalcemia (total serum calcium > 3.0 mmol/L); allergic reactions to vitamin D medications; 25(OH)D level more than 60 ng/mL (determined by immunochemiluminescence analysis). All patients were recruited in the period from October 2019 to April 2021. The study protocol (ClinicalTrials.gov Identifier: NCT04844164) was approved by the Ethics Committee of Endocrinology Research Centre, Moscow, Russia on 10 April 2019 (abstract of record No. 6), all patients signed informed consent to participate in the study.
All participants received standard therapeutic dose (150,000 IU) of an aqueous solution of cholecalciferol (Aquadetrim®, Medana Pharma S.A., Sieradz, Poland) orally as a single dose [34]. Blood and urine samples were obtained before the intake as well as on days 1, 3 and 7 after administration; time points of sample collection were determined based on the authors’ previous work evaluating changes in 25(OH)D levels after a therapeutic dose of cholecalciferol [35]. The assessment included serum biochemical parameters (total calcium, albumin, phosphorus, creatinine, magnesium), parathyroid hormone (PTH), vitamin D-binding protein (DBP), vitamin D metabolites (25(OH)D3, 25(OH)D2, 1,25(OH)2D3, 3-epi-25(OH)D3 and 24,25(OH)2D3), free 25(OH)D and urine biochemical parameters (calcium- and phosphorus-creatinine ratios in spot urine).

2.2. Socio–Demographic and Anthropometric Data Collection

At the baseline visit, patients underwent a questionnaire aimed to assess their lifestyle: the presence of unhealthy habits, physical activity level, balanced diet (consumption of dairy products, meat, coffee, soft drinks), exposure to ultraviolet (UV) radiation (solarium and sunscreen usage, traveling south and the number of daytime walks in the sunny weather in the 3 months preceding study participation). Smoking status was classified as current smoker, former smoker and non-smoker; current and former smokers were collectively referred to as total smokers. A unit of alcohol was defined as a glass of wine, a bottle of beer or a shot of spirits, approximating 10–12 g ethanol. Serving of dairy products was defined as 100 g of cottage cheese, 200 mL of milk, 125 g of yogurt or 30 g of cheese. Patients’ weight was measured in light indoor clothing with a medical scale to the nearest 100 g, and their height with a wall-mounted stadiometer to the nearest centimeter. BMI was calculated as weight in kilograms divided by height in meters squared.

2.3. Laboratory Measurements

Morning ACTH (reference range 7–66 pg/mL), serum cortisol after a low-dose dexamethasone suppression test (cutoff value for suppression, 50 nmol/L [36]), late-night salivary cortisol (reference range 0.5–9.4 nmol/L [37]) were assayed by electrochemiluminescence assay using a Cobas 6000 Module e601 (Roche, Rotkreuz, Switzerland). The 24-h UFC (reference range 60–413 nmol/24 h) was measured by an immunochemiluminescence assay (extraction with diethyl ether) on a Vitros ECiQ (Ortho Clinical Diagnostics, Raritan, NJ, USA).
Total 25(OH)D levels (25(OH)D2 + 25(OH)D3; reference range 30–100 ng/mL) at the baseline visit were determined by the immunochemiluminescence analysis (Liaison, DiaSorin, Saluggia, Italy). PTH levels were evaluated by the electrochemiluminescence immunoassay (ELECSYS, Roche, Basel, Switzerland; reference range for this and subsequent laboratory parameters are given in the Results section for easier reading). Biochemical parameters of blood serum and urine were assessed by the ARCHITECT c8000 analyzer (Abbott, Chicago, IL, USA) using reagents from the same manufacturer according to the standard methods. Serum DBP and free 25(OH)D levels were measured by enzyme-linked immunosorbent assay (ELISA) using commercial kits. The assay used for free 25(OH)D levels assessment (DIAsource, ImmunoAssays S.A., Ottignies-Louvain-la-Neuve, Belgium) has <6.2% intra- and inter-assay coefficient of variation (CV) at levels 5.8–9.6 pg/mL. The assay used for DBP levels assessment (Assaypro, St Charles, MO, USA) has 6.2% average intra-assay CV and 9.9% average inter-assay CV.
The levels of vitamin D metabolites (25(OH)D3, 25(OH)D2, 1,25(OH)2D3, 3-epi-25(OH)D3 and 24,25(OH)2D3) in serum were determined by ultra-high performance liquid chromatography in combination with tandem mass spectrometry (UPLC-MS/MS) using an in-house developed method, described earlier [38]. With this technique, the laboratory participates in DEQAS quality assurance program (lab code 2388) and the results fall within the target range for the analysis of 25(OH)D and 1,25(OH)2D metabolites in human serum (Supporting Information, Figures S1 and S2). All UPLC-MS/MS measurements were made after the first successful completion (5/5 samples within the target range) of the DEQAS distributions for both analytes simultaneously. Each batch contained control samples (analytes in blank serum) with both high and low analyte concentrations. The samples were barcoded and randomized prior to the measurements to eliminate analyst-related errors.
Serum samples (3 aliquots) collected at each visit were either transferred directly to the laboratory for biochemical analyzes, total 25(OH)D and PTH measurement (1 aliquot) or were stored at −80 °C avoiding repeated freeze-thaw cycles for measurement of DBP, free 25(OH)D and vitamin D metabolites at a later date (2 aliquots).
Albumin-adjusted serum calcium levels were calculated using the formula [39]: total plasma calcium (mmol/L) = measured total plasma calcium (mmol/L) + 0.02 × (40 − measured plasma albumin (g/L)).
Baseline free 25(OH)D levels were also calculated using the formula introduced by Bikle et al. [40,41]. The affinity constant for 25(OH)D and albumin binding (Kalb) used for the calculation was equal 6 × 105 M−1, and affinity constant for 25(OH)D and DBP binding (KDBP) was equal 7 × 108 M−1.

Free 25(OH)D=total 25(OH)D1+Kalbalbumin+KDBPDBP

2.4. Statistical Analysis

Statistical analysis was performed using Statistica version 13.0 (StatSoft, Tulsa, OK, USA). All data were analyzed with non-parametric statistics and expressed as median [interquartile range] unless otherwise specified. Mann-Whitney U-test and Fisher’s exact two-tailed test were used for comparisons between two groups. Friedman ANOVA was performed to evaluate changes in indices throughout the study and pairwise comparisons using Wilcoxon test with adjustment for multiple comparisons (Bonferroni) were also made if the Friedman ANOVA was significant. Spearman rank correlation method was used to obtain correlation coefficients among indices. A p-value of less than 0.05 was considered statistically significant. When adjusting for multiple comparisons, a p-value greater than the significance threshold, but less than 0.05 was considered as a trend towards statistical significance.

3. Results

The groups were similar in terms of age, sex and BMI (p > 0.05). Both groups consisted predominantly of young and middle-aged women and the majority of patients were overweight or moderately obese (Table 1). Patients from the study group presented with lower screening levels of total 25(OH)D (p < 0.05).
Table 1. General characteristics of the patients at the baseline visits. For detailed description of the data format please refer to the Section 2.
The features of the underlying disease course in the study group are listed in Table 2. 15 patients (50%) had diabetes mellitus with an almost compensated state at the time of participation in the study, and 7 patients (23%) reported a history of low-energy fractures.
Table 2. Characteristics of the patients with Cushing’s disease (CD) in terms of the underlying disease.
The groups did not differ significantly in the reported smoking status, the level of daily physical activity, dietary habits and UV exposure (p > 0.05) and although there was a slight difference in alcohol consumption (p < 0.05), the absolute values were minor in both groups (Table 3).
Table 3. Questionnaire results.

3.1. Baseline Laboratory Evaluation

Detailed results of laboratory studies are presented in Table 4 and Table 5.
Table 4. Changes in the levels of the biochemical parameters and parathyroid hormone (PTH) during the study.
Table 5. Changes in the levels of free 25(OH)D, vitamin D-binding protein (DBP) and vitamin D metabolites during the study.
Patients with CD had several alterations in biochemical parameters, in particular, lower baseline serum creatinine and albumin levels, while magnesium levels were higher than in the control group (p < 0.05). They also had higher levels of urine phosphorus-creatinine ratio (p < 0.05). The rest of the studied biochemical parameters did not show significant difference between the groups (p > 0.05). 3 patients (10%) from the study group and 5 patients (17%) from the control group had secondary hyperparathyroidism, one patient with CD (3%) was diagnosed with mild primary hyperparathyroidism.
As for the assessment of vitamin D metabolism, unexpectedly the levels of 25(OH)D3 occurred to be equal in the groups (p > 0.05), with only two patients (7%) from the study group and one patient (3%) from the control group having sufficient vitamin D levels, according to the Endocrine Society and the Russian Association of Endocrinologists guidelines (≥30 ng/mL [34,42]). The levels of the active vitamin D metabolite—1,25(OH)2D3—were equal between the groups as well (p > 0.05), whereas the levels of 3-epi-25(OH)D3 and 24,25(OH)2D3 were lower in CD patients. Further calculation of 25(OH)D3/24,25(OH)2D3 and 25(OH)D3/1,25(OH)2D3 ratios corresponded to the observed levels of metabolites: 25(OH)D3/24,25(OH)2D3 ratio was higher in the study group (p < 0.05) assuming lower 24-hydroxylase activity and 25(OH)D3/1,25(OH)2D3 ratio was equal between the groups (p > 0.05).
Levels of free 25(OH)D were lower in CD patients (p < 0.05) and the levels of DBP did not differ between the groups (p > 0.05). Although calculated free 25(OH)D showed prominent positive correlation with the measured free 25(OH)D in both groups (r = 0.63 in the study group, r = 0.87 in the control group, p < 0.05), the association appeared to be weaker in the study group. In the control group, DBP levels correlated with both measured and calculated 25(OH)D levels (r = −0.48, p < 0.05 and r = −0.69, p < 0.05 respectively), while in patients with CD there was no association with measured free 25(OH)D levels (r = 0.04, p > 0.05 and r = −0.50, p < 0.05 respectively).
Correlation with 24-h UFC in CD patients was observed for serum albumin level (r = −0.37, p < 0.05) and urine calcium-creatinine ratio (r = 0.51, p < 0.05) among assessed biochemical parameters, and only with 25(OH)D3/24,25(OH)2D3 ratio among the parameters of vitamin D metabolism (r = 0.36, p < 0.05).

3.2. Laboratory Evaluation after the Intake of Cholecalciferol

All patients from the study group and 28 patients (93%) from the control group completed the study.
The observed baseline differences in biochemical parameters mostly preserved during the follow-up. In the study group there was an increase in serum phosphorus levels by Day 1 (p = 0.006) and a tendency to an increase in the urine phosphorus-creatinine ratio by Day 7 (p = 0.02). Patients from the control group showed a clinically insignificant increase in serum creatinine levels by Day 1 (p = 0.002) and a non-significant trend towards an increase in serum total and albumin-adjusted calcium (p = 0.01 for both measurements). No change in PTH levels was observed in patients with CD during the follow-up (p > 0.05), while in the control group there was a tendency for PTH to decrease by Day 3 (p = 0.02). There were no new cases of hypercalcemia in both groups during the follow-up. One patient from the study group and one patient from the control group had persistently increased urine calcium-creatinine ratio throughout the study. Four patients from the study group (13%) and none from the control group developed hypercalciuria during the follow-up, however these patients had no clinical manifestations during the observation period.
By Day 7, 25 patients (83%) from the study group and 22 patients (79%) reached sufficient 25(OH)D3 levels (≥30 ng/mL). Levels of 25(OH)D3 continued to increase by Day 3 in both groups (p < 0.001), after which tended to decrease in the study group (p = 0.01) and remained stable in the control group (p = 0.65). The increase in 25(OH)D3 after cholecalciferol intake was equal between the groups (18.5 [15.9; 22.5] ng/mL in the study group vs. 16.6 [13.1; 19.8] ng/mL in the control group, p > 0.05). In the presence of obesity, Δ25(OH)D3 was higher in the CD patients than in the control group (18.3 [14.2; 23.0] vs. 12.1 [10.0; 13.1] ng/mL, p < 0.05), while in non-obese patients no difference was observed (p > 0.05).
Obese and non-obese patients with CD had equal Δ25(OH)D3 (18.3 [14.2; 23.0] vs. 19.6 [16.0; 21.5] ng/mL, p > 0.05), while in the control group it was significantly lower in obese patients (12.1 [10.0; 13.1] vs. 18.3 [15.3; 21.4] ng/mL, p < 0.05). BMI showed significant correlation with Δ25(OH)D3 only in the control group (r = −0.47, p < 0.05), while in CD patients there was no such association (r = −0.06, p > 0.05) (Figure 1).
Figure 1. Relationship between Δ25(OH)D3 and BMI in groups.
1,25(OH)2D3 levels increased in CD patients by Day 1 and were stable during the follow-up in the control group. The rest of the studied parameters of vitamin D metabolism changed in a similar way between groups: 3-epi-25(OH)D3 levels increased until the Day 3, after which they decreased by the Day 7; 24,25(OH)2D3 levels showed more graduate elevation throughout the follow-up. In both groups 25(OH)D3/24,25(OH)2D3 ratios increased by Day 1, after which they decreased by Day 7, and 25(OH)D3/1,25(OH)2D3 ratios increased by Day 1, after which they remained stable. DBP levels didn’t change and free 25(OH)D levels showed an increase in both groups during the follow-up. The levels of 25(OH)D2 did not exceed 0.5 ng/mL in all examined individuals throughout the study. Among assessed parameters of vitamin D metabolism, higher 25(OH)D3/24,25(OH)2D3 ratios in the study group was the only difference between the groups which remained significant throughout the observation period (p < 0.05) (Figure 2).
Figure 2. Dynamic evaluation of 25(OH)D3/24,25(OH)2D3 ratios in groups.

4. Discussion

The main goal of our study was to evaluate the 25(OH)D3 levels and its response to the therapeutic dose of cholecalciferol in patients with CD as compared to healthy individuals. We observed no difference in baseline 25(OH)D3 assessed by UPLC-MS/MS between groups. Similar to our data were obtained in most studies conducted specifically in the state of endogenous hypercortisolism in humans [12,15] and dogs [14]. The study by Kugai et al. lacked control group and reported plasma levels of 25(OH)D corresponding to the vitamin D deficiency in most of the examined patients [10], while in our study only 2/3 of the patients with CD had 25(OH)D levels below 20 ng/mL. As for exogenous hypercortisolism, the meta-analysis aimed to explore serum 25(OH)D levels in glucocorticoid users showed lower levels than in healthy controls, but similar to steroid-naive disease controls, thus causing concern regarding the influence of the disease status on 25(OH)D levels [24]. Somewhat surprisingly, we obtained significantly discordant results in the study group when screening total 25(OH)D by ELISA and when measuring baseline 25(OH)D3 by UPLC-MS/MS, since the initial difference between the groups revealed by ELISA data with lower total 25(OH)D levels in the study group was not replicated by UPLC-MS/MS. It should be noted that our ELISA method did not participate in an external quality control program at the time of the study unlike UPLC-MS/MS; furthermore, a lower analytical performance was previously described for this technique with tendency for low specificity and lower measurement results [45].
When assessing other parameters of vitamin D metabolism, the most significant finding was the higher 25(OH)D3/24,25(OH)2D3 ratio in CD patients, both initially and during the observation after the intake of the cholecalciferol loading dose, indicating consistently reduced activity of 24-hydroxylase, the main enzyme of vitamin D catabolism. Earlier clinical and experimental studies also suggested altered activity of enzymes of vitamin D metabolism in hypercortisolism. However, these studies were heterogeneous and aimed predominantly at studying the activity of 1α-hydroxylase [7,8,10,11,12,14], which was not altered in patients with CD as compared to healthy individuals in our study. In the setting of the short-term glucocorticoid administration, Lindgren et al. showed transient increase in 24,25(OH)2D3 levels in rats [8], while in the study of Hahn et al. there was no change in 24,25(OH)2D3 levels [11]. Dogs with CD had similar 24,25(OH)2D3 levels before and after hypophysectomy as well as compared to control dogs [14]. The only study of considerably similar design by Kugai et al. reported low-normal 24,25(OH)2D3 in patients with Cushing’s syndrome [10], which is consistent with our result, as well as some experimental works indicative of suppression on CYP24A1 expression by glucocorticoids in human osteoblasts [23], liver and intestine [21] and in rat brain and myocardium [22]. However, in the present work, the activity of 24-hydroxylase in patients with hypercortisolism was for the first time evaluated by calculating the 25(OH)D3/24,25(OH)2D3 ratio, which has recently emerged as a new tool for vitamin D status assessment [46,47]. Given the correlation of this parameter with laboratory marker of the underlying disease activity (24-h UFC), a direct effect of cortisol overproduction on 24-hydroxylase activity might be assumed. Interestingly, it seems that the decreased activity of 24-hydroxylase observed in CD influenced the effectiveness of cholecalciferol treatment, decreasing the negative effect of obesity, as patients with CD had similar increase in 25(OH)D3 in obese and non-obese state and lacked correlation between Δ25(OH)D3 and BMI, as opposed to the control group. Moreover, the increase in 25(OH)D3 in obese patients from the control group was lower not only than in non-obese controls, but also than in obese patients with CD.
Another intriguing finding was lower levels of free 25(OH)D observed in patients with CD despite similar DBP levels and lower albumin levels, which, on the contrary, allows one to expect higher values of free 25(OH)D. Considering the weaker correlation between the measured and calculated free 25(OH)D in patients with CD, as well as the lack of correlation of the measured 25(OH)D with the main transport protein, an altered affinity of DBP might be suspected. One possible explanation is protein glycosylation as a consequence of diabetes mellitus, which was present in half of the patients [38,48,49]. After cholecalciferol intake, which was accompanied by an increase in free 25(OH)D, the differences between the groups were leveled; therefore, another suggested explanation might be competitive binding to the ligand. Since actin binds DBP with high affinity [50] and considering catabolic action of glucocorticoids on muscle tissue [51], actin is a presumable competing ligand candidate. Although this is mostly speculative, as far as the authors are aware, the present work was the first to assess free vitamin D in the glucocorticoid excess, so the described findings require verification of reproducibility and further evaluation.
The obtained discrepancies in the biochemical parameters characterizing calcium and phosphorus metabolism were generally consistent with the data of early studies discussed in the introduction [12,25,26,27,28,29], except for similar to controls serum phosphorus levels and lower prevalence of hypercalciuria. An interesting observation was the complete absence of the PTH decrease in patients with CD after receiving a loading dose of cholecalciferol. The mechanism of this phenomenon is not entirely clear, we tend to agree with the earlier hypothesis that this may be an adaptation to chronic urinary calcium loss [52].
Our research is distinguished by a number of important strengths: a prospective design, substantial sample of patients with CD, accounting for social and behavioral factors affecting vitamin levels D, comprehensive spectrum of vitamin D metabolism parameters investigated and participation in an external quality control program for vitamin D metabolites measurement.
Nevertheless, the study also had several limitations: the amount of dietary vitamin D and phosphorus, as well as possible differences in DBP affinity to vitamin D metabolites due to genetic isoforms of DBP [53] or other possible involved parameters (e.g., fibroblast growth factor-23) were not taken into account. A few patients from both groups received therapy with possible impact on vitamin D and calcium metabolism within 3 months preceding the participation in the study (spironolactone, diuretics, proton pump inhibitors, oral contraceptives, antifungal treatment, antidepressants, barbiturates, antiepileptic drugs). The groups had a trend for differences in sex and BMI (p = 0.07 for both parameters). Also, the study lacked a study group of patients with remission of CD to test the hypotheses put forward, however, this is a promising direction for further research.

5. Conclusions

We report that patients with endogenous ACTH-dependent hypercortisolism of pituitary origin have a consistently higher 25(OH)D3/24,25(OH)2D3 ratio than healthy controls, which is indicative of a decrease in 24-hydroxylase activity. This altered activity of the principal vitamin D catabolism might influence the effectiveness of cholecalciferol treatment. There is also a lack of clarity regarding the lower levels of free 25(OH)D observed in patients with CD, which require further study. To test the proposed hypotheses and to develop specialized clinical guidelines for these patients, longer-term randomized clinical trials are needed.

Supplementary Materials

The following are available online at https://www.mdpi.com/article/10.3390/nu13124329/s1, Method validation against DEQAS, Figure S1: Comparison between DEQAS data for 25(OH)D scheme and our lab results, Figure S2: Comparison between DEQAS data for 1,25(OH)2D scheme and our lab results.

Author Contributions

Conceptualization, L.R., E.P., A.P. and A.Z.; methodology, V.B., Z.B., L.R. and G.M.; formal analysis, A.P.; investigation, A.P., V.B., E.P., L.D. and A.Z.; data curation, A.P. and V.B.; writing—original draft preparation, A.P.; writing—review and editing, V.B., E.P., A.Z., Z.B., L.R.; visualization, V.B.; supervision, L.D., L.R., G.M. and N.M.; project administration, L.R. and N.M.; funding acquisition, L.R. and N.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Russian Science Foundation, grant number 19-15-00243.

Institutional Review Board Statement

This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of Endocrinology Research Centre, Moscow, Russia on 10 April 2019 (abstract of record No. 6).

Informed Consent Statement

Written informed consent was obtained from all individual participants included in the study.

Data Availability Statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Acknowledgments

We express our deep gratitude to our colleagues: Natalya M. Malysheva, Vitaliy A. Ioutsi, Larisa V. Nikankina for the help with the laboratory research.

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

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