Blunted response to prolactin stimulation tests and evaluation of L-dopa depression inpatients with hyperprolactinemic galactorrhea

Abstract

Thirty-two patients with galactorrhea were subjected to serum prolactin (PRL) stimulation and suppression tests in comparison to a control group (no. 6, mean basal PRL: 7.9 ng/ml). Nine of them had pituitary microadenomas (MIG) (mean basal PRL: 63.4 ng/ml), 9 macroadeno-mas (MAC) (mean basal PRL: 273.4 ng/ml) and 14 idiopathic or drug induced galactorrhea, of which 8 with normal basal prolactinemia (NPRL, mean basal PRL: 9.5 ng/ml) and 6 with basal hy-perprolactinemia (HPRL, mean basal PRL: 36.9 ng/ml). Stimulation with thyrotropin — releasing hormone (TRH) increased PRL concentration to a mean peak values of 48.5,99.0 and 369.9 ng/ml in the control, MIC and MAC groups respectively. The results of adenoma patients expressed as the mean percentual increment of the peak PRL serum corrected for basal levels (Δ %) were significantly lower than in control group (MIC: 68.2%, MAC: 49.4%, control 597.2%). Stimulation with chlorpromazine (CPZ) produced a rise in PRL concentrations, reaching mean peak values of 32.7 ng/ml in normals, 102.0 ng/ml in MIC and 337.6 ng/ml in MAC. The mean Δ % of the response to CPZ in the tumor patients was significantly blunted in comparison to normals (control: 541.9%, MIC: 86.7% and MAC: 89.8%). In comparison to the control subjects, the HPRL similarly to the tumoral group of patients showed a blunted Δ % responses to TRH and CPZ whereas the NPRL group was not statistically different. No difference was seen in the L-dopa depression test among all groups of patients (NPRL, HPRL, MIC and MAC). These data suggest: 1) Basal PRL value is the determinant of the responsiveness to stimulation tests, higher basal PRL values inducing a lower degree of responsiveness; 2) Dynamic tests of prolactin secretion are unhelpful to distinguish the tumoral group from other hyperprolactinemic patients because of considerable overlap.