Medical treatment of Cushing's syndrome: glucocorticoid receptor antagonists and mifepristone

Mifepristone is the first and only available glucocorticoid receptor antagonist. It was initially mainly considered as a so-called 'contragestive' pill due to its antiprogestin activity. In this review, we summarize the results of mifepristone reported in the literature as a treatment of Cushing's syndrome. Most of the patients were treated due to unsuccessful surgery and/or partially effective anticortisolic drugs. The majority of them presented a rapid decrease of clinical signs of hypercortisolism during the first month of treatment; about half experienced a reduction in their elevated blood pressure, and half of the diabetic patients presented improved blood glucose levels. Mifepristone treatment has 2 main drawbacks: (1) the blockade of glucocorticoid receptors leads to increased ACTH and cortisol levels, making it difficult to adapt the treatment and diagnose adrenal deficiency, and (2) increased cortisol levels can also lead to severe hypokalemia. Follow-up of efficacy should only be clinical (weight, blood pressure, skin lesions) and biological (regular blood potassium sampling). Dose adjustment will be performed based on these parameters. The lack of a large available prospective cohort of patients on mifepristone, and the scarcity of data on its long-term effects, does not allow recommending it as a first-line drug in the treatment of hypercortisolism. However, as mifepristone is a rapidly effective drug, it can play a role in the management of hypercortisolism. The main indication is the partial efficacy or bad tolerance of other well-known anticortisolic drugs, either by replacement (bad tolerance, lack of effectiveness) or addition (multimodal approach) of mifepristone.