A 38-year-old woman was admitted to our hospital because of amenorrhea, multiple bone fractures, and a Cushingoid appearance. Endocrinological investigations revealed that she had co-existing Cushing's disease and prolactinoma, with a serum level of prolactin (PRL) at 1,480 ng/mL, corticotropin (ACTH) at 81.3 pg/mL, and cortisol at 16.6 μg/dL. Due to the lack of indication for transsphenoidal surgery, cabergoline monotherapy was initiated. A 6-month course of treatment resulted in only subtle amelioration of hypercortisolism, while hyperprolactinemia was dramatically improved. In 5 cases of bihormonal (ACTH/PRL) pituitary macroadenoma reported in the English literature, 2 were initially treated with dopaminergic agonists with substantial effectiveness for both PRL and ACTH. We herein report an extremely rare case of bihormonal macroadenoma in which only PRL was responsive to treatment.
