Different dopaminergic control of plasma luteinizing hormone, follicle-stimulating hormone and prolactin in ovulatory and postmenopausal women: effect of ovariectomy

The main aim of this study was to evaluate the effect of dopamine infusion on plasma luteinizing hormone (LH), follicle-stimulating hormone, (FSH) and prolactin (PRL) after acute (1 week postovariectomy) and chronic (postmenopausal women) estrogen withdrawal. We also studied the same group of postmenopausal women after ovariectomy to evaluate the possible influence of other gonadal factors on the endocrine effects of dopamine. In order to have a further indication of neuroendocrine dopamine activity on pituitary secretions, we measured the change in plasma LH, FSH and PRL after the administration of metoclopramide, a dopamine receptor antagonist. Our findings confirm that in fertile women dopamine infusion inhibits plasma LH and FSH levels and show that 1 week after ovariectomy the LH decrease during dopamine administration is still present whereas the FSH decrease is not. In all groups of patients, dopamine significantly inhibited plasma PRL levels. Metoclopramide increased plasma LH levels in reproductive-age women before ovariectomy, but not in postmenopausal women. Plasma FSH levels did not change in any group and PRL levels increased after metoclopramide administration in all subjects. The present findings show that dopamine regulation of LH is impaired in long-term menopause, but not shortly after ovariectomy. These changes in LH control are not followed by similar changes in PRL secretion, which remains under tonic inhibitory regulation by dopamine. The different behavior of LH and FSH after ovariectomy and in postmenopause shows the independence of LH and FSH regulation