Functional Characterization of Hypothalamic Hyperprolactinemia*

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Abstract
PRL secretory dynamics were evaluated by severalstimulation and suppression tests in nine patients withhyperprolactinemia due to organic hypothalamic disease. BasalPRL levels ranged between 20–63 ng⁄ml. There was a normalPRL response to TRH in eight cases (i.e. doubling of basallevels), whereas none of the seven tested subjects responded tosulpiride. The same dissociation of responses was not observedin any of the patients who were still hyperprolactinemic aftersurgery. Concomitant dopamine infusion resulted in sulpirideinduced PRL release in the four subjects so studied. None of 50 other hyperprolactinemic patients (11 withmacroprolactinoma, 18 with microprolactinoma, and 21 withidiopathic hyperprolactinemia) showed PRL response to TRHbut not to sulpiride. The TRH-induced PRL increase was significantlyhigher than that induced by sulpiride in hypothalamichyperprolactinemia and significantly lower in idiopathic diseaseas well as in healthy controls; no differences were found inprolactinoma patients. The administration of substances resulting in stimulation ofpituitary dopamine receptors, such as dopamine and L-dopa,induced a normal PRL suppression in 7 patients with hypothalamicdisease so tested, whereas central nervous system-actingdopaminergic drugs, such as carbidopa plus L-dopa and nomifensine,failed to lower PRL levels in most cases (even whennormoprolactinemic after surgery). These data suggest that themild to moderate hyperprolactinemia found in many patientswith hypothalamic lesions is due to dopamine deficiency at thepituitary level, that TRH and dopamine receptors at the lactotropesare intact in this condition, and that paired TRH andsulpiride tests may be of some diagnostic utility in hyperprolactinemicpatients. They further suggest that subjects with socalledidiopathic hyperprolactinemia do not suffer from the typeof hypothalamic derangement exhibited by patients with organiclesions of the hypothalamus. (J Clin Endocrinol Metab55: 897,1982)