The value of the thyrotropin-releasing hormone test in patients with prolactin-secreting pituitary tumors and suprasellar non-pituitary tumors.

The prolactin (PRL) response to thyrotropin-releasing hormone (TRH) (delta PRL) was normal in 7 (18%) of 38 patients with clinical evidence of a prolactinoma. A negative percentage correlation between basal PRL and delta PRL was found (P less than 0.05), but a percentage correlation between tumor size and delta PRL was absent. In a survey of literature concerning 548 patients, delta PRL after TRH administration amounted to 100% or more of the basal value in 11% of patients with clinical evidence of a prolactinoma and in 9% with an adenoma proven by surgery. Hyperprolactinemia was also present in 12 of our 21 patients (57%) with suprasellar tumors not related to pituitary tumors. In 7 of 11 of these hyperprolactinemic patients (64%), the PRL response to TRH was decreased. In conclusion, the TRH test may be helpful but is not decisive in the diagnostic work-up of hyperprolactinemia patients.