Dynamic evaluation of prolactin secretion by successive TRH and metoclopramide stimulations

[True and false hyperprolactinemia: how to discriminate one from the other in infertility management?]

Serum prolactin measurement is usually performed in infertility evaluation, even if there's no specific clinical presentation of hyperprolactinemia. High levels of prolactin are noted in 20 to 30% of menstrual abnormalities and in about 10% of regular menses. It is of importance to determine whether hyperprolactinemia is related to pituitary adenoma, drug administration, general diseases, or circulating large forms of prolactin, in order to avoid heavy, expensive, time consuming and unnecessary clinical investigations or therapeutic actions. We must first to confirm the biological diagnosis of hyperprolactinemia with few repeated plasmatic measurements, and, later, if necessary use TRH-metoclopramide test and/or pituitary magnetic resonance imaging.

Effects of metoclopramide and quipazine on serum prolactin concentrations in steers

The dopamine antagonist metoclopramide monohydrochloride (MC) and the serotonin agonist quipazine maleate (Q) were administered to steers by both the oral and intravenous (i.v.) routes. Dose-response studies were designed to determine the effects of these drugs on serum prolactin (PRL) concentrations. Parameters subjected to analysis included maximal serum PRL concentrations within 1 h and the areas under the PRL response curves over time. At 1, 4, and 8 mg/kg i.v., and at 15, 30, 45, and 60 mg/kg orally, MC increased (P less than 0.05) serum PRL concentrations (difference between maximal and basal serum PRL concentrations) and increased (P less than 0.05) areas under the PRL response curves except for 1.0 mg/kg i.v. Doses of MC greater than 60 mg/kg and Q at all dosage rates were considered toxic. These studies determined a dose-response to MC in terms of serum PRL concentration and indicate that MC is well tolerated and effective for elevating serum PRL concentrations in steers. Furthermore, 4 mg/kg i.v. and 15 mg/kg orally could be considered the preferred dosage rates due to a plateau in the response above those rates.

Histiocytosis X of the hypothalamus

An unusual case of cutaneous and hypothalamic histiocytosis X (HX) is reported. The hypothalamic involvement occurred as a tumor that mimicked a chiasm glioma on computed tomography angioscanning. Magnetic resonance imaging after gadolinium injection localized the tumor within the third ventricle floor. The HX origin of the tumor was confirmed by histological examination of hypothalamic biopsies obtained by transventricular endoscopy. The results of endocrine evaluation were consistent with anterior panhypopituitarism resulting from a multiple releasing-hormone secretory defect, but there was no diabetes insipidus. This unusual endocrine aspect has not been previously described in the field of hypothalamic HX. Lastly, the tumor was insensitive to low dose megavoltage radiation therapy. This unusual case stresses the superiority of magnetic resonance imaging over computed tomography scanning in the assessment of suprasellar tumors and emphasizes the usefulness of transventricular endoscopy in these cases.

Effect of clomiphene citrate on prolactin and gonadotropin release during GnRH-analog treatment

The capacity of the anterior pituitary to secrete prolactin (PRL) and gonadotropins was evaluated by TRH and GnRH stimulation, followed by metoclopramide (MC) administration 1 hour later, before and after clomiphene citrate (CC) priming in 8 endometriosis patients receiving GnRH agonist analog (Buserelin) therapy for 6 months. GnRH-analog treatment lowered the maximal PRL responses to TRH and MC stimulation in the luteal phase, compared to those of 8 normally menstruating control patients. The LH response to GnRH stimulation was also diminished, indicating pituitary desensitization, while the FSH response remained unchanged. Antiestrogen administration during GnRH-analog treatment further reduced the capacity of pituitary lactotropes to secrete PRL in TRH and MC tests, and it increased the LH response but not the FSH response to GnRH stimulation. These data suggest that CC affects the mechanisms controlling PRL and gonadotropin secretions in hypoestrogenic women after prolonged GnRH agonist analog treatment by different modes of action, the action on gonadotropes being stimulatory and that on lactotropes inhibitory.

Flunarizine increases PRL secretion in normal and in migraineous women

Flunarizine (FLU) treatment has proved effective for migraine but there have been reports--though controversial--of depression and/or extrapyramidal signs and symptoms in cases of chronic therapy. It has been suggested that FLU may interfere with the activity of central dopaminergic systems. In this study, prolactin (PRL) secretion was chosen as a parameter for functional exploration of central dopaminergic systems in normal and migraineous women before and after FLU treatment. Five healthy women were given FLU (20 mg) and placebo per os, each for one day. A significance increase of serum PRL levels was found after FLU administration, but not after placebo. Ten women with common migraine underwent TRH stimulation test (200 micrograms i.v.) before and after a 30-day FLU therapy (10 mg per os). Basal PRL levels were not modified by the treatment, but TRH stimulated PRL values were significantly enhanced after a 30-day FLU therapy. These results seem to confirm the hypothesis that FLU interferes with central dopaminergic activity.

Anterior pituitary dysfunction during the luteal phase following ovarian hyperstimulation

The capacity of the pituitary to secrete prolactin (PRL) and gonadotropins was investigated during the luteal phase of eight normally menstruating tubal infertility patients after ovarian stimulation with clomiphene citrate, human menopausal gonadotropin, and human chorionic gonadotropin. The baseline values of PRL were significantly higher (P less than 0.025), those of luteinizing hormone unchanged, and those of follicle-stimulating hormone lower (P less than 0.025) during the treatment than in the control cycles. The maximal response of PRL to the dopamine antagonist metoclopramide was increased (P less than 0.01), whereas the maximal responses of luteinizing hormone (P less than 0.025) and follicle-stimulating hormone (P less than 0.001) to gonadotropin-releasing hormone were lowered in the treatment cycles. The current results indicate that ovarian hyperstimulation with clomiphene citrate/human menopausal gonadotropin/human chorionic gonadotropin may induce luteal phase pituitary dysfunction, which may affect the luteal phase functions of the corpus luteum.

Depressed follicle-stimulating hormone, luteinizing hormone, and prolactin responses to the luteinizing hormone-releasing hormone, thyrotropin-releasing hormone, and metoclopramide test in endurance runners in the hard-training season

The responses of serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) to luteinizing hormone-releasing hormone (LH-RH) and the responses of prolactin (PRL) to thyrotropin-releasing hormone (TRH) and metoclopramide (MC) were measured in the late luteal phase of the cycle in 12 endurance runners and 11 control women and in 12 joggers and 7 control women. LH-RH (100 micrograms) and TRH (200 micrograms) were injected intravenously at the beginning of the test, and MC (10 mg) was injected 60 minutes later. Blood samples were obtained before and 20, 60, 80, and 120 minutes after the beginning of the test. Runners had significantly lower serum concentrations of estradiol and progesterone than control subjects, whereas the concentrations of FSH, LH, and PRL were similar at the beginning of the study. Compared with their controls, the runners had significantly lower FSH (P less than 0.05) and LH responses at 20 minutes (P less than 0.05) and lower LH responses at 80 minutes (P less than 0.01) to LH-RH and lower PRL responses to MC 20 minutes after MC injection (P less than 0.05). Joggers and their control subjects had similar LH, FSH, and PRL responses to these pharmacologic stimuli. It is concluded that decreased ovarian activity explains, at least partly, the lowered responses of FSH and LH to LH-RH and the lowered response of PRL to MC in endurance runners.