Development of Nelson's syndrome in a patient with recurrent Cushing's disease. Analysis of secretory behavior of the pituitary tumor.

A markedly cushingoid 32-year-old man presented to Queens Hospital Center with headache, hyperpigmentation, and visual field loss. Twelve years earlier, he had undergone subtotal adrenalectomy for Cushing's disease, but symptoms of hypercortisolemia promptly recurred. Workup revealed the presence of a large, expanding intrasellar mass, plasma ACTH levels between 3,000 and 10,000 pg/ml, and markedly elevated cortisol levels. The secretion of ACTH (mainly ACTH 1-39-like peptide) by the pituitary tumor showed neither diurnal periodicity nor response to a variety of pharmacologic agents known to affect ACTH secretion. The patient demonstrates a rarely observed presentation of Nelson's syndrome, with aggressive adrenotropic pituitary tumor growth even in the presence of chronic hypercortisolemia.