A 22-year-old nulliparous woman presented with primary amenorrhea, primary hypothyroidism, hyperprolactinemia, and radiologic evidence of pituitary enlargement. Investigation demonstrated limited reserves of ACTH and growth hormone. Circulating concentrations of TSH and prolactin were elevated; they increased in response to thyrotropin releasing hormone and decreased following L-dopa administration. After treatment with L-tri-iodothyronine, serum TSH and prolactin levels fell markedly, reserves of growth hormone and ACTH returned to normal, menstrual periods began, and the patient conceived. She experienced an uncomplicated prenatal, intrapartum, and postpartum course. It is thought that this patient represents a distinct clinical entity: a syndrome of amenorrhea, hyperprolactinemia, and pituitary enlargement, all secondary to primary thyroid failure. This syndrome should be distinguished from the Forbes-Albright syndrome, as it is reversible with thyroid replacement therapy. Recognition of this syndrome may thus spare the patient unnecessary, and potentially dangerous, pituitary surgery or irradiation.