HYPOGONADISM, GALACTORRHOEA AND HYPER-PROLACTINAEMIA: EVALUATION OF PITUITARY GONADOTROPHINS RESERVE BEFORE AND UNDER BROMOCRIPTINE

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Abstract
Twenty patients with hypogonadism (19 women with amenorrhea and 1 man with impotence and infertility), galactorrhea and hyper-prolactinemia (range: 36-344 ng/ml) were studied. The radiological study of the sella turcica, including in all cases hypocycloidal tomograms, allowed classification of the patients into 3 groups: group I (n = 4) had a grossly enlarged sella turcica; group II (n = 12) had localized alterations indicating the probable existence of a prolactin-secreting microadenoma (microdeformation), while group III patients presented no radiological abnormality. Before treatment, all 5 patients were submitted to a complete evaluation of the function of their anterior pituitary, including the LH [luteinizing hormone] and FSH [follicle stimulating hormone] responses to i.v. administration of Gn-RH [gonadotropin-releasing hormone]. All group I patients had low basal LH levels and a blunted response to Gn-RH. The basal LH and in response to Gn-RH were normal in most of the group II patients and in all of the group III patients. An exaggerated FSH response to Gn-RH was observed in 6/12 patients with microdeformation (group II) but not in groups I and III patients. A low LH and a blunted LH response to Gn-RH is highly suggestive of the existence of a pituitary prolactin-secreting adenoma in case of amenorrhea and hyperprolactinemia patients; a normal response does not rule out such a diagnosis. The reasons for an exaggerated FSH response to Gn-RH in patients with suspected prolactin-secreting microadenoma remain to be investigated, though this pattern can also occur in other cases of amenorrhea. The Gn-RH test might contribute to the assessment of the hypothalamo-pituitary axis of patients with hyperprolactinemia. Six patients treated for 4 mo. with bromocriptine (CB-154) were submitted to reevaluation of their pituitary gonadotropins reserve. All the women experienced restoration of menses with 39 days of treatment, and the male patient regained potency. Bromocriptine treatment and subsequent normalized prolactin levels in the 4 group II women tested were associated with normalization of their previously exaggerated FSH response to Gn-RH; LH responses were also diminished in these cases. The hypothesis that hyperprolactinemia per se could interfere with the endogenous secretion of Gn-RH at the hypothalamic level was supported. In 1 patient with grossly a enlarged sella turcica and a previous lack of an LH and FSH response to Gn-RH, bromocriptine treatment restored a normal gonadotropins response, confirming that, in this case, the alteration of this response was indeed due to a prolonged lack of endogenous Gn-RH secretion.