Increase in Glucose Uptake by Cushing’s Disease-associated Tumors Could Improve Early Detection

Posted on October 13, 2017 by MaryO

An increase in glucose uptake by Cushing’s disease-associated pituitary tumors could improve their detection, new research shows.

The study, “Corticotropin releasing hormone can selectively stimulate glucose uptake in corticotropinoma via glucose transporter 1,” appeared in the journal Molecular and Cellular Endocrinology.

The study’s senior author was Dr. Prashant Chittiboina, MD, from the Department of Neurosurgery, Wexner Medical Center, The Ohio State University, in Columbus, Ohio.

Microadenomas – tumors in the pituitary gland measuring less than 10 mm in diameter – that release corticotropin, or corticotropinomas, can lead to Cushing’s disease. The presurgical detection of these microadenomas could improve surgical outcomes in patients with Cushing’s.

But current tumor visualization methodologies – magnetic resonance imaging (MRI) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) – failed to detect a significant percentage of pituitary microadenomas.

Stimulation with corticotropin-releasing hormone (CRH), which increases glucose uptake, has been suggested as a method of increasing the detection of adenomas with 18F-FDG PET, by augmenting the uptake of 18F-FDG – a glucose analog.

However, previous studies aiming to validate this idea have failed, leading the research team to hypothesize that it may be due to a delayed elevation in glucose uptake in corticotropinomas.

The scientists used clinical data to determine the effectiveness of CRH in improving the detection of corticotropinomas with 18F-FDG PET in Cushing’s disease.

They found that CRH increased glucose uptake in human and mouse tumor cells, but not in healthy mouse or human pituitary cells that produce the adrenocorticotropic hormone (ACTH). Exposure to CRH increased glucose uptake in mouse tumor cells, with a maximal effect at four hours after stimulation.

Similarly, the glucose transporter GLUT1, which is located at the cell membrane, was increased two hours after stimulation, as was GLUT1-mediated glucose transport.

These findings indicate a potential mechanism linking CRH exposure to augmented glucose uptake through GLUT1. Expectedly, the inhibition of glucose transport with fasentin suppressed glucose uptake.

The researchers consistently observed exaggerated evidence of GLUT1 in human corticotropinomas. In addition, human corticotroph tumor cells showed an increased breakdown of glucose, which indicates that, unlike healthy cells, pituitary adenomas use glucose as their primary source of energy.

Overall, the study shows that corticotropin-releasing hormone (CRH) leads to a specific and delayed increase in glucose uptake in tumor corticotrophs.

“Taken together, these novel findings support the potential use of delayed 18F-FDG PET imaging following CRH stimulation to improve microadenoma detection in [Cushing’s disease],” researchers wrote. The scientists are now conducting a clinical trial to further explore this promising finding.

From https://cushingsdiseasenews.com/2017/10/12/glucose-uptake-in-cushings-disease-could-improve-presurgical-tumor-detection/

Filed under: Clinical trials, Cushing's, pituitary | Tagged: , , , , , , , , , , , , , , , | Leave a comment »

Macroadenoma biochemical behavior in pediatric patients with Cushing’s disease differs from adult cases

Posted on May 15, 2015 by MaryO

Cushing’s disease in children is associated with similar biochemical measures whether the disease is due to macroadenomas or microadenomas, according to a presentation at the AACE 24th Annual Scientific & Clinical Congress.

This contrasts with the disease behavior in adults, in whom macrodenomas demonstrate less glucocorticoid suppression and adrenocorticotropic hormone (ACTH) response to laboratory tests than do microadenomas, according to researchers.

“Children with pituitary macroadenomas are more likely to have the classical response to Cushing’s disease functional testing as microadenomas,”Ricardo Correa, MD, a clinical and research endocrinology fellow at National Institutes of Health, told Endocrine Today.

Correa and colleagues conducted a retrospective review of patients with Cushing’s disease who were younger than 18 years when they were admitted to the NIH between 1997 and 2014. All Cushing’s diagnoses were confirmed by pathology.

Pituitary macroadenoma was identified in 13 patients (69% female) and microadenoma in 74 (58% female). The groups had similar mean age (14 years) and BMI (31.8 kg/m2 and 30.2 kg/m2 for macroadenoma and microadenoma, respectively). The macroadenoma group had a median (25% to 75%) 24-hour urine free cortisol of  263.60 mcg/24 hr (range 170.7-528) compared with 371.6 mcg/ 24 hr (range 244.2-625.3) in the microadenoma group (P = 0.47). Median 24-hr urinary 17-hydroxysteroid excretion in the macroadenoma group was 12.6 mg/24 hr (range 8.9-42.5) and 31.6 mg/24 hr (range 4.3-39.9) in the microadenoma group.

Mean morning serum cortisol was 38.9 ± 40.4 mcg/dL compared with  20.2 ± 15.8 mcg/dL in the macroademona and microadenoma groups, respectively (P = 0.16). Mean morning basal plasma ACTH was 106.3 ± 112.3 pg/mL compared with 49.9±44.3 pg/mL for the macroadenoma and microadenoma groups, respectively (P = 0.11), while ACTH responses to the ovine corticotropin-releasing hormone test revealed no statistically significant differences. Using the high dose dexamethasone suppression test, 58% (7/12) suppressed more than 69% in the macroadenoma group compared to 69% (44/64) in the microadenoma group (P = .51).

“Studies in adult patients have demonstrated that macroadenomas have less glucocorticoid suppressibility after the high-dose dexamethasone suppression test and attenuated ACTH response to CRH compared to pituitary microadenomas,” according to Correa. “However, the present study shows that this is not true in children; although patients with macroadenomas had a tendency for higher baseline serum ACTH and cortisol levels, their responses to dynamic testing were similar to those with microadenomas.”

Reference:

Correa R, et al. Abstract #803. Presented at: AACE 24th Annual Scientific & Clinical Congress; May 13-17, 2015; Nashville, Tenn.

Disclosure: The researchers report no relevant financial disclosures.

From http://www.healio.com/endocrinology/adrenal/news/online/%7Bb4fbf36f-ac88-4eff-9278-90f0a8d1aec2%7D/macroadenoma-biochemical-behavior-in-pediatric-patients-with-cushings-disease-differs-from-adult-cases?sc_trk=internalsearch

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