The Physiology Of Hypercortisolism

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Endogenous pathologic hypercortisolism, or Cushing's syndrome, is associated with poor quality of life, morbidity, and increased mortality. Early diagnosis may mitigate against this natural history of the disorder. The clinical presentation of Cushing's syndrome varies, in part related to the extent and duration of cortisol excess. When hypercortisolism is severe, its signs and symptoms are unmistakable. However, most of the signs and symptoms of Cushing's syndrome are common in the general population (e.g., hypertension and weight gain) and not all are present in every patient. In addition to classical features of glucocorticoid excess, such as proximal muscle weakness and wide purple striae, patients may present with the associated comorbidities that are caused by hypercortisolism. These include cardiovascular disease, thromboembolic disease, psychiatric and cognitive deficits, and infections. As a result, internists and generalists must consider Cushing's syndrome as a cause, and endocrinologists should search for and treat these comorbidities. Recommended tests to screen for Cushing's syndrome include 1 mg dexamethasone suppression, urine free cortisol, and late night salivary cortisol. These may be slightly elevated in patients with physiologic hypercortisolism, which should be excluded, along with exogenous glucocorticoid use. Each screening test has caveats and the choice of tests should be individualized based on each patient's characteristics and lifestyle. We have also found that thyroid functions may be abnormal in Cushing's syndrome and must be interpreted with care in patients taking exogenous glucocorticoids.