Mild Cases of Cushing's Syndrome Present Diagnostic Challenges
Medication is the most common cause of Cushing's syndrome. Image credit: CNRI/Science Source
In the early 20th century, the term "pluriglandular syndrome" was coined by Harvey Cushing to describe the disorder that results from chronic tissue exposure to excessive levels of glucocorticoids.1 Now called Cushing's syndrome, the condition affects an estimated 10-15 million people annually, most often women and individuals between the ages of 20 and 50 years.2 Risk factors and common comorbidities include hypertension, obesity, osteoporosis, uncontrolled diabetes, depression, and anxiety.3
The clinical presentation of the disorder is heterogenous and varies by sex, age, and disease severity. Common signs and symptoms include central adiposity, roundness of the face or extra fat around the neck, thin skin, impaired short-term memory and concentration, irritability, hirsutism in women, fatigue, and menstrual irregularity.4 Because each of these features may be observed in a wide range of other conditions, it may be difficult to diagnose cases that are not severe.
"It can be challenging to differentiate the milder forms from pseudo-Cushing's states," which are characterized by altered cortisol production and many of the same clinical features as Cushing's syndrome, according to Roberto Salvatori, MD, the medical director of the Johns Hopkins Pituitary Center, Baltimore, Maryland. These may include alcoholism, obesity, eating disorders, and depression. "Because Cushing's can cause depression, for example, it is sometimes difficult to determine which came first," he says. In these states, however, hypercortisolism is believed to be driven by increased secretion of hypothalamic corticotropin-releasing hormone, which is suppressed in Cushing's syndrome.5
Causes and Diagnosis
If Cushing's syndrome is suspected on the basis of the patient's physical appearance, the diagnostic workup should include a thorough medical history, physical exam, and 1 or more of the following tests to establish hypercortisolism: the 24-hour urinary cortisol test, the low-dose dexamethasone suppression test, or the late-night salivary cortisol test. "We sometimes use 2 or 3 of these tests since 1 may not accurately reflect cortisol production in a particular patient," Dr Salvatori notes. The next step is to determine the source of the hypercortisolism, which may involve the high-dose dexamethasone suppression test, magnetic resonance imaging, or petrosal sinus sampling.2
Medication is the most common cause of Cushing's syndrome. These iatrogenic or exogenous cases typically result from corticosteroids administered for conditions such as asthma, allergies, and autoimmune disorders.6 More rarely, the disorder can be caused by the use of medroxyprogesterone. In these cases, corticosteroids should be reduced or discontinued under medical care, if possible.
Endogenous Cushing's syndrome results from the presence of benign or malignant tumors on the adrenal or pituitary glands or elsewhere in the body. These tumors can interfere with the adrenal glands' production of cortisol that is usually prompted by the adrenocorticotropic hormone (ACTH) released by the pituitary gland.6 There are 3 different mechanisms by which the process can occur.
- Pituitary adenomas, which account for approximately 70% of endogenous cases of Cushing's syndrome, secrete ACTH and stimulate additional cortisol production. Because of the large proportion of cases this condition represents, it is specifically referred to as Cushing's disease. It is more common in women than men (with a ratio of 3 to 4:1), although in pediatric patients, it occurs more frequently in boys vs girls.5
- Adrenal tumors (adenomas, malignant tumors, or micronodular hyperplasia) produce cortisol in their own tissue in addition to the amount produced by the adrenal glands. These tumors, which cause approximately 15% of endogenous Cushing's syndrome cases, are more common in children vs adults and in women vs men.
- Benign or malignant tumors elsewhere in the body, most often the lungs, thyroid, thymus, and pancreas, secrete ACTH and trigger the excessive release of cortisol. An estimated 15% of endogenous cases are attributed to these types of tumors.
Surgery is the first-line treatment for Cushing's syndrome. "We first want to try to figure out the cause of the disorder," Dr Salvatori says. "Ideally, treatment involves surgery to remove the tumor that is causing it."
When surgery is unsuccessful, contraindicated, or delayed, other treatment options include radiation or medications that inhibit cortisol, modulate the release of ACTH, or inhibit steroidogenesis.5 Bilateral adrenalectomy may be indicated for patients who do not respond to medication or other surgery.
If surgical resection of the tumor is successful, then "all of the comorbidities reverse, but if it is unsuccessful or must be delayed, you would treat each comorbidity" with the appropriate medication; for example, antihypertensives for high blood pressure and antidiabetic medications for diabetes, Dr Salvatori advises. In severe cases, prophylactic antibiotics may be indicated for the prevention of severe infections such as pneumonia.
It is also important to inquire about and address psychiatric symptoms related to Cushing's syndrome, even in patients who are in remission. It has been proposed that the chronic hypercortisolism and dysfunction of the HPA axis may "lead to structural and functional changes in the central nervous system, developing brain atrophy, particularly in the hippocampus, which may determine the high prevalence of psychiatric disorders, such as affective and anxiety disorders or cognitive dysfunctions," according to a recently published paper on the topic.7 Patients should be screened with self-report questionnaires such as the Beck Depression Inventory and the Hospital Anxiety and Depression Scale, and management of psychiatric symptoms may include patient education, psychotropic medications, and referral to a mental health professional.
Several trials are currently planned or underway, including a phase 2 randomized, double-blind, placebo-controlled study of an oral medication called ATR-101 by Millendo Therapeutics, Inc. (ClinicalTrials.gov identifier: NCT03053271). In addition to the need for novel medical therapies, refined imaging techniques could improve surgical success rates in patients with Cushing's disease in particular, according to Dr Salvatori. "A significant portion of these patients have tumors too small to be detected by MRI, and the development of more sensitive MRI could improve detection and provide a surgical target" for neurosurgeons treating the patients, he says.
Milder cases of Cushing's syndrome present diagnostic challenges are a result overlapping features with various other conditions. Diagnosis may require careful observation as well as biochemical and imaging tests.
- Loriaux DL. Diagnosis and differential diagnosis of Cushing's syndrome. N Engl J Med. 2017;376:1451-1459. doi:10.1056/NEJMra1505550
- American Association of Neurological Surgeons. Cushing's syndrome/disease. http://www.aans.org/Patients/Neurosurgical-Conditions-and-Treatments/Cushings-Disease. Accessed August 1, 2017.
- León-Justel A, Madrazo-Atutxa A, Alvarez-Rios AI, et al. A probabilistic model for cushing's syndrome screening in at-risk populations: a prospective multicenter study. J Clin Endocrinol Metab. 2016;101:3747-3754. doi:10.1210/jc.2016-1673
- The Pituitary Society. Cushing's syndrome and disease–symptoms. https://pituitarysociety.org/patient-education/pituitary-disorders/cushings/symptoms-of-cushings-disease-and-cushings-syndrome. Accessed August 1, 2017.
- Sharma ST, Nieman LK, Feelders RA. Cushing's syndrome: epidemiology and developments in disease management. Clin Epidemiol. 2015;7:281-293. doi:10.2147/CLEP.S44336
- National Institutes of Health: Eunice Kennedy Shriver National Institute of Child Health and Human Development. What causes Cushing's syndrome? https://www.nichd.nih.gov/health/topics/cushing/conditioninfo/pages/causes.aspx. Accessed August 1, 2017.
- Santos A, Resmini E, Pascual JC, Crespo I, Webb SM. Psychiatric symptoms in patients with Cushing's syndrome: prevalence, diagnosis and management. Drugs. 2017;77:829-842. doi:10.1007/s40265-017-0735-z