Diagnostic difficulties in periodic Cushing's syndrome.

A 22-year-old black woman presented with symptoms suggestive of Cushing's syndrome three years after chemotherapy for a presumed teratoma with cervical lymphadenopathy. Initially, the absence of clinical signs and the demonstration of two normal 24 h urinary free cortisols appeared to exclude the diagnosis, but an ectopic adrenocorticotropin-producing thymic carcinoid was subsequently removed surgically. Cushing's syndrome due to ectopic adrenocorticotropin production can be difficult to diagnose, particularly if there is periodic hormonogenesis.