Rebound elevation of cortisol following cyproheptadine withdrawal in Cushing's disease from a pituitary macroadenoma.

A 44-year-old female with Cushing's disease associated with a pituitary macroadenoma was treated with cyproheptadine, 24 mg per day, after partial surgical resection of the tumor. A large residual tumor remained. There was no clear suppression of serum and urinary cortisol during therapy, but both levels rose markedly to beyond pre cyproheptadine levels, on withdrawal of the drug. This is the first report on the use of cyproheptadine in Cushing's disease associated with a pituitary macroadenoma. The response in this patient indicates an influence of cyproheptadine on ACTH secretion by the macroadenoma.