Prolactin response to thyrotropin-releasing hormone (TRH) in patients with hypothalamic-pituitary disease

The prolactin (PRL) response to thyrotropin-releasing hormone (TRH) was evaluated in 686 patients over a 4-year period. Of the 170 control subjects tested, none had a blunted PRL response to TRH. Eighty patients with prolactinomas documented by surgery were tested. Ninety-five percent (76 of 80) of these patients had an abnormally blunted PRL response to TRH. Of the 87 patients with a prolactinoma who did not undergo surgery, 98% (85 of 87) had a blunted PRL response to TRH. Many patients with other pituitary and hypothalamic diseases (pituitary tumors other than prolactinomas [Cushing's disease, acromegaly, chromophobe adenoma], craniopharyngioma) also had an abnormal PRL response to TRH (79 of 153, 52%). In the majority of patients with hyperprolactinemia due to dopamine antagonist medications, TRH stimulation did not produce a normal rise in PRL. The TRH test may be helpful in confirming the diagnosis of prolactinoma, but it is not a decisive factor in the diagnosis or management of this entity.