Cushing’s Syndrome: A Tale of Frequent Misdiagnosis


What is it?

Cushing’s syndrome is a condition you probably have never heard of, but for those who have it, the symptoms can be quite scary.  Worse still, getting it diagnosed can take a while.  Cushing’s syndrome occurs when the tissues of the body are exposed to high levels of cortisol for an extended amount of time. Cortisol is the hormone the body produces to help you in times of stress. It is good to have cortisol at normal levels, but when those levels get too high it causes health problems.  Although cortisol is related to stress, there is no evidence that Cushing’s syndrome is directly or indirectly caused by stress.

Cushing’s syndrome is considered rare, but that may be because it is under-reported. As a result, we don’t have good estimates for how many people have it, which is why the estimates for the actual number of cases vary so much–from 5 to 28 million people.[1] The most common age group that Cushing’s affects are those 20 to 50 years old.  It is thought that obesity, type 2 diabetes, and high blood pressure may increase your risk of developing this syndrome.[2]

What causes Cushing’s Syndrome?

Cushing’s syndrome is caused by high cortisol levels. Cushing’s disease is a specific form of Cushing’s syndrome. People with Cushing’s disease have high levels of cortisol because they have a non-cancerous (benign) tumor in the pituitary gland.  The tumor releases adrenocorticotropin hormone (ACTH), which causes the adrenal glands to produce excessive cortisol.

Cushing’s syndrome that is not Cushing’s disease can be also caused by high cortisol levels that result from tumors in other parts of the body.  One of the causes is “ectopic ACTH syndrome.” This means that the hormone-releasing tumor is growing in an abnormal place, such as the lungs or elsewhere.  The tumors can be benign, but most frequently they are cancerous. Other causes of Cushing’s syndrome are benign tumors on the adrenal gland (adrenal adenomas) and less commonly, cancerous adrenal tumors (adrenocortical carcinomas). Both secrete cortisol, causing cortisol levels to get too high.

In some cases, a person can develop Cushing’s syndrome from taking steroid medications, such as prednisone. These drugs, known as corticosteroids, mimic the cortisol produced by the body. People who have Cushing’s syndrome from steroid medications do not develop a tumor.[3]

What are the signs and symptoms of Cushing’s Syndrome?

The appearance of people with Cushing’s syndrome starts to change as cortisol levels build up. Regardless of what kind of tumor they have or where the tumor is located, people tend to put on weight in the upper body and abdomen, with their arms and legs remaining thin; their face grows rounder (“moon face”); they develop fat around the neck; and purple or pink stretch marks appear on the abdomen, thighs, buttocks or arms. Individuals with the syndrome usually experience one or more of the following symptoms: fatigue, muscle weakness, high glucose levels, anxiety, depression, and high blood pressure. Women are more likely than men to develop Cushing’s syndrome, and when they do they may have excess hair growth, irregular or absent periods, and decreased fertility.[4]

Why is Cushing’s Syndrome so frequently misdiagnosed?

These symptoms seem distinctive, yet it is often difficult for those with Cushing’s syndrome to get an accurate diagnosis.  Why?  While Cushing’s is relatively rare, the signs and symptoms are common to many other diseases. For instance, females with excess hair growth, irregular or absent periods, decreased fertility, and high glucose levels could have polycystic ovarian syndrome, a disease that affects many more women than Cushing’s.   Also, people with metabolism problems (metabolic syndrome), who are at higher than average risk for diabetes and heart disease, also tend to have abdominal fat, high glucose levels and high blood pressure.[5]

Problems in testing for Cushing’s

When Cushing’s syndrome is suspected, a test is given to measure cortisol in the urine. This test measures the amount of free or unbound cortisol filtered by the kidneys and then released over a 24 hour period through the urine. Since the amount of urinary free cortisol (UFC) can vary a lot from one test to another—even in people who don’t have Cushing’s—experts recommend that the test be repeated 3 times. A diagnosis of Cushing’s is given when a person’s UFC level is 4 times the upper limit of normal.  One study found this test to be highly accurate, with a sensitivity of 95% (meaning that 95% of people who have the disease will be correctly diagnosed by this test) and a specificity of 98% (meaning that 98% of  people who do not have the disease will have a test score confirming that).[6] However, a more recent study estimated the sensitivity as only between 45%-71%, but with 100% specificity.[7]  This means that the test is very accurate at telling people who don’t have Cushing’s that they don’t have it, but not so good at identifying the people who really do have Cushing’s.  The authors that have analyzed these studies advise that patients use the UFC test together with other tests to confirm the diagnosis, but not as the initial screening test.[8]  

Other common tests that may be used to diagnose Cushing’s syndrome are: 1) the midnight plasma cortisol and late-night salivary cortisol measurements, and 2) the low-dose dexamethasone suppression test (LDDST).  The first test measures the amount of cortisol levels in the blood and saliva at night.  For most people, their cortisol levels drop at night, but people with Cushing’s syndrome have cortisol levels that remain high all night. In the LDDST, dexamethasone is given to stop the production of ACTH.  Since ACTH produces cortisol, people who don’t have Cushing’s syndrome will get lower cortisol levels in the blood and urine. If after giving dexamethasone, the person’s cortisol levels remain high, then they are diagnosed with Cushing’s.[9]

Even when these tests, alone or in combination, are used to diagnose Cushing’s, they don’t explain the cause. They also don’t distinguish between Cushing’s syndrome, and something called pseudo-Cushing state.

Pseudo-Cushing state

Some people have an abnormal amount of cortisol that is caused by something unrelated to Cushing’s syndrome such as polycystic ovarian syndrome, depression, pregnancy, and obesity. This is called pseudo-Cushing state.  Their high levels of cortisol and resulting Cushing-like symptoms can be reversed by treating whatever disease is causing the abnormal cortisol levels. In their study, Dr. Giacomo Tirabassi and colleagues recommend using the desmopressin (DDAVP) test to differentiate between pseudo-Cushing state and Cushing’s.  The DDAVP test is especially helpful in people who, after being given dexamethasone to stop cortisol production, continue to have moderate levels of urinary free cortisol (UFC) and midnight serum cortisol.[10]

An additional test that is often used to determine if one has pseudo-Cushing state or Cushing’s syndrome is the dexamethasone-corticotropin-releasing hormone (CRH) test. Patients are injected with a hormone that causes cortisol to be produced while also being given another hormone to stop cortisol from being produced. This combination of hormones should make the patient have low cortisol levels, and this is what happens in people with pseudo-Cushing state.  People with Cushing’s syndrome, however, will still have high levels of cortisol after being given this combination of hormones.[11]

How can Cushing’s be treated?

Perhaps because Cushing’s is rare or under-diagnosed, few treatments are available. There are several medications that are typically the first line of treatment.  None of the medications can cure  Cushing’s, so they are usually taken until other treatments are given to cure Cushing’s, and only after that if the other treatment fails.

The most common treatment for Cushing’s disease is transsphenoidal surgery, which requires the surgeon to reach the pituitary gland through the nostril or upper lip and remove the tumor.  Radiation may also be used instead of surgery to shrink the tumor.  In patients whose Cushing’s is caused by ectopic ACTH syndrome, all cancerous cells need to be wiped out through surgery, chemotherapy, radiation or a variety of other methods, depending on the location of the tumor. Surgery is also recommended for adrenal tumors.  If Cushing’s syndrome is being caused by corticosteroid (steroid medications) usage, the treatment is to stop or lower your dosage.[12]

Medications to control Cushing’s (before treatment or if treatment fails)

According to a 2014 study in the Journal of Clinical Endocrinology and Metabolism, almost no new treatment options have been introduced in the last decade. Researchers and doctors have focused most of their efforts on improving existing treatments aimed at curing Cushing’s. Unfortunately, medications used to control Cushing’s prior to treatment and when treatment fails are not very effective.

Many of the medications approved by the FDA for Cushing’s syndrome and Cushing’s disease, such as pasireotide, metyrapone, and mitotane, have not been extensively studied.  The research presented to the FDA by the makers of these three drugs did not even make clear what an optimal dose was.[13] In another 2014 study, published in Clinical Epidemiology, researchers examined these three same drugs, along with ten others, and found that only pasireotide had moderate evidence to support its approval.  The other drugs, many of which are not FDA approved for Cushing’s patients, had little or no available evidence to show that they work.[14] They can be sold, however, because the FDA has approved them for other diseases.  Unfortunately, that means that neither the FDA nor anyone else has proven the drugs are safe or effective for Cushing patients.

Pasireotide, the one medication with moderate evidence supporting its approval, caused hyperglycemia (high blood sugar) in 75% of patients who participated in the main study for the medication’s approval for Cushing’s.  As a result of developing hyperglycemia, almost half (46%) of the participants had to go on blood-sugar lowering medications. The drug was approved by the FDA for Cushing’s anyway because of the lack of other effective treatments.

Other treatments used for Cushing’s have other risks.  Ketoconazole, believed to be the most commonly prescribed medications for Cushing’s syndrome, has a black box warning due to its effect on the liver that can lead to a liver transplant or death.  Other side effects include: headache, nausea, irregular periods, impotence, and decreased libido. Metyrapone can cause acne, hirsutism, and hypertension. Mitotane can cause neurological and gastrointestinal symptoms such as dizziness, nausea, and diarrhea and can cause an abortion in pregnant women.[15]

So, what should you do if you suspect you have Cushing’s Syndrome?

Cushing’s syndrome is a serious disease that needs to be treated, but there are treatment options available for you if you are diagnosed with the disease. If the symptoms in this article sound familiar, it’s time for you to go see your doctor. Make an appointment with your general practitioner, and explain your symptoms to him or her.  You will most likely be referred to an endocrinologist, who will be able to better understand your symptoms and recommend an appropriate course of action.

 

All articles are reviewed and approved by Dr. Diana Zuckerman and other senior staff.

  1. Nieman, Lynette K. Epidemiology and clinical manifestations of Cushing’s syndrome, 2014. UpToDate: Wolters Kluwer Health
  2. Cushing’s syndrome/ disease, 2013. American Association of Neurological Surgeons. http://www.aans.org/Patient%20Information/Conditions%20and%20Treatments/Cushings%20Disease.aspx
  3. Cushing’s syndrome, 2012. National Endocrine and Metabolic Diseases: National Institutes of Health. http://endocrine.niddk.nih.gov/pubs/cushings/cushings.aspx#treatment
  4. Cushing’s syndrome, 2012. National Endocrine and Metabolic Diseases: National Institutes of Health. http://endocrine.niddk.nih.gov/pubs/cushings/cushings.aspx#treatment
  5. Cushing’s syndrome, 2012. National Endocrine and Metabolic Diseases: National Institutes of Health. http://endocrine.niddk.nih.gov/pubs/cushings/cushings.aspx#treatment
  6. Newell-Price, John, Peter Trainer, Michael Besser and Ashley Grossman. The diagnosis and differential diagnosis of Cushing’s syndrome and pseudo-Cushing’s states, 1998. Endocrine Reviews: Endocrine Society
  7. Carroll, TB and JW Findling. The diagnosis of Cushing’s syndrome, 2010. Reviews in Endocrinology and Metabolic Disorders: Springer
  8. Ifedayo, AO and AF Olufemi. Urinary free cortisol in the diagnosis of Cushing’s syndrome: How useful?, 2013. Nigerian Journal of Clinical Practice: Medknow.
  9. Cushing’s syndrome, 2012. National Endocrine and Metabolic Diseases: National Institutes of Health. http://endocrine.niddk.nih.gov/pubs/cushings/cushings.aspx#treatment
  10. Tirabassi, Giacomo, Emanuela Faloia, Roberta Papa, Giorgio Furlani, Marco Boscaro, and Giorgio Arnaldi. Use of the Desmopressin test in the differential diagnosis of pseudo-Cushing state from Cushing’s disease, 2013. The Journal of Clinical Endocrinology & Metabolism: Endocrine Society.
  11. Cushing’s syndrome, 2012. National Endocrine and Metabolic Diseases: National Institutes of Health. http://endocrine.niddk.nih.gov/pubs/cushings/cushings.aspx#treatment
  12. Cushing’s syndrome, 2012. National Endocrine and Metabolic Diseases: National Institutes of Health. http://endocrine.niddk.nih.gov/pubs/cushings/cushings.aspx#treatment
  13. Tirabassi, Giacomo, Emanuela Faloia, Roberta Papa, Giorgio Furlani, Marco Boscaro, and Giorgio Arnaldi. Use of the Desmopressin test in the differential diagnosis of pseudo-Cushing state from Cushing’s disease, 2013. The Journal of Clinical Endocrinology & Metabolism: Endocrine Society.
  14. Galdelha, Monica R. and Leonardo Vieira Neto. Efficacy of medical treatment in Cushing’s disease: a systematic review, 2014. Clinical Endocrinology: John Wiley & Sons.
  15. Adler, Gail. Cushing syndrome treatment & management, 2014. MedScape: WebMD.

Adapted from https://www.center4research.org/cushings-syndrome-frequent-misdiagnosis/

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