Impaired luteinizing hormone responsiveness to gonadotropin-releasing hormone in the inferior petrosal sinuses of hyperprolactinemic patients.

The aim of this study was to evaluate serum baseline and gonadotropin-releasing hormone (GnRH)-stimulated follicle-stimulating hormone (FSH) and luteinizing hormone (LH) concentrations in the inferior petrosal sinuses and in peripheral blood in nine normoprolactinemic and eight hyperprolactinemic patients who were being subjected to perihypophyseal phlebography for diagnostic purposes or neurosurgical indications. Serum FSH and LH concentrations were significantly higher in both inferior petrosal sinuses than in peripheral blood (p < 0.001 and p < 0.05, respectively) in normoprolactinemic but not in hyperprolactinemic patients. Additionally, in normoprolactinemic patients, the LH response to intravenous bolus GnRH in the inferior petrosal sinuses (evaluated as peak/basal) was significantly greater than in hyperprolactinemic patients (p < 0.01). No difference was found as far as FSH response to GnRH was concerned. In conclusion, these findings suggest that the hypogonadism of hyperprolactinemic patients may depend on the impaired release of LH at the pituitary level.