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GILLIAN C. L. LACHELIN, SALIM ABU-FADIL, SAMUEL S. C. YEN, Functional Delineation of Hyperprolactinemic-Amenorrhea, The Journal of Clinical Endocrinology & Metabolism, Volume 44, Issue 6, 1 June 1977, Pages 1163–1174, https://doi.org/10.1210/jcem-44-6-1163
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Abstract
To account for the development of PRL hypersecretion and acyclic gonadotropin release, the separate functional activity of the pituitary and the ovary were assessed in two overlapping groups of patients with amenorrhea-galactorrhea and comparable levels of hyperprolactinemia. Group I was composed of 13 patients with a ‘probable’ microadenoma and Group II was composed of 5 patients with surgically documented pituitary PRL-secreting microadenomata. Pituitary functional capacity was determined by alternating pulses of LRF (10 μg) and TRF (200 μg)—3 doses of each. When responses in the early follicular phase (EF) of normal women were used as a reference point, there appeared to be a progressive decline in pituitary LH sensitivity (Δ max to 1st pulse) as well as reserve (net integrated release during 2nd and 3rd pulses) from Group I to Group II patients. In contrast, there was an increase in pituitary sensitivity and reserve for FSH in both groups of patients. Hence, there exists a marked reduction of the LH/FSH ratio of the releasable gonadotropin of the pituitary. These functional aberrations were associated with normal basal concentrations of LH and FSH except in Group II patients in whom significantly lower levels of FSH were found. Basal E2 levels were significantly lower in both groups of patients. Under these conditions, the integrated (6 h) gonadotropin release induced by LRF appears to be biologically active as evidenced by an impressive rise in circulating E2 levels. The smaller integrated gonadotropin release in Group II patients was associated with a correspondingly smaller increase in E2 levels. This finding strongly suggests that in humans, the presence of hyperprolactinemia, other than in the postpartum period, may not have a measurable effect on the ovarian response to endogenous gonadotropin stimulation. Basal TSH and its response to TRF was normal but PRL responses to TRF were markedly impaired in Group I and absent in Group II patients. These functional aberrations in the three reproductive hormones—LH FSH and PRL—can be readily reversed by the reduction ot PRL secretion either through an increase in dopamine activity such as the administration of 2-Bromo-α-ergocryptine (a dopamine agonist) or by the removal of the microadenoma by microsurgery. Based on previous experimental data and the functional changes in the pituitary and ovary observed in this study, we suggest that a primary defect in the pituitary lactotrophs — hypothalamic dopamine system results in hyperprolactinemia, acyclic gonadotropin secretion, and pituitary microadenoma.
