Cyproheptadine treatment of Nelson's syndrome: restoration of plasma ACTH circadian periodicity and reversal of response to TRF.

Administration of cyproheptadine for four months to a patient with Nelson's Syndrome was associated with evidence of skin lightening, decreased plasma ACTH concentrations, return of a normal circadian periodicity of plasma ACTH concentrations, and lack of responsiveness of plasma ACTH concentrations to TRF administration, in contrast to the response seen in the untreated state.