The effects on the ovulatory cycle of metoclopramide-induced increased prolactin levels during follicular development

Prolactin suppresses GnRH but not TSH secretion

BACKGROUND/AIMS

In animal models, prolactin increases tuberoinfundibular dopamine turnover, which has been demonstrated to suppress both hypothalamic GnRH and pituitary TSH secretion. To test the hypothesis that prolactin suppresses GnRH and TSH secretion in women, as preliminary evidence that a short-feedback dopamine loop also operates in the human, the effect of hyperprolactinemia on GnRH and TSH secretion was examined.

METHODS

Subjects (n=6) underwent blood sampling every 10 min in the follicular phase of a control cycle and during a 12-hour recombinant human prolactin (r-hPRL) infusion preceded by 7 days of twice-daily subcutaneous r-hPRL injections. LH and TSH pulse patterns and menstrual cycle parameters were measured.

RESULTS

During the 7 days of r-hPRL administration, baseline prolactin increased from 16.0+/-3.0 to 101.6+/-11.6 microg/l, with a further increase to 253.7+/-27.7 microg/l during the 12-hour infusion. LH pulse frequency decreased (8.7+/-1.0 to 6.0+/-1.0 pulses/12 h; p<0.05) with r-hPRL administration, but there were no changes in LH pulse amplitude or mean LH levels. There were also no changes in TSH pulse frequency, mean or peak TSH. The decreased LH pulse frequency did not affect estradiol, inhibin A or B concentrations, or menstrual cycle length.

CONCLUSION

These studies demonstrate that hyperprolactinemia suppresses pulsatile LH secretion but not TSH secretion and suggest that GnRH secretion is sensitive to hyperprolactinemia, but that TSH secretion is not. These data further suggest that the degree of GnRH disruption after 7 days of hyperprolactinemia is insufficient to disrupt menstrual cyclicity.

Prolactin disorders

OBJECTIVE

To review the pathophysiology, clinical manifestations, current diagnostic procedures, and treatment options for disorders involving PRL production. Common clinical dilemmas are discussed in a pragmatic fashion to guide the practitioner.

DESIGN

A world literature search of basic sciences and medical articles from the last three decades was performed using computerized MEDLINE. Recent endocrine and reproductive endocrine textbooks also were reviewed. Studies were selected for their degree of contribution to the basic sciences and clinical understanding of the disorder and for the quality of their study design and content. The information was summarized and grouped according to its relevance and application to specific sections of the manuscript. Studies were evaluated and critically used to support the views of the authors and to suggest specific clinical management strategies.

RESULT(S)

Disorders derived from abnormal PRL production are relatively common in clinical practice. Infertility, menstrual disorders, and galactorrhea are the most frequent manifestations encountered in women. Although frequently benign, the disorder occasionally may have severe consequences.

CONCLUSION(S)

An understanding of the underlying physiology and pathophysiology coupled with the awareness of the heterogeneous presentation of this disorder should help the clinician to approach it successfully.

The effect of a specific emotional stressor on prolactin, cortisol, and testosterone concentrations in women varies with their trait anxiety

The psychological and the hormonal response to a specific emotional stressor (a video film on treatment of infertility, pregnancy, and delivery) was investigated in 30 women and the responses were correlated with their trait anxiety level. The experiment included a resting period before and after the stressor. The psychological response, i.e., the change in state anxiety, was in phase with the stressor and varied with the trait anxiety level. The endocrinological response, i.e., the time courses of prolactin, cortisol, and testosterone, was not in phase but varied with the trait anxiety level. It is suggested that psychological phenomena as anticipation, mental assimilation, and reflection could explain these findings, and that these should be taken into account when investigating the so-called "psychological" infertility.

Transient hyperprolactinemia during cycle stimulation: influence on the endocrine response and fertilization rate of human oocytes and effects of bromocriptine treatment

The effect of transient hyperprolactinemia and its treatment during cycle stimulation on the endocrine response and fertilization rate of human oocytes was studied. Fifty stimulated cycles were included in the study and divided into three groups: group I consisted of 18 cycles with serum prolactin (PRL) levels less than or equal to 25 ng/ml; group II contained 15 cycles, where patients developed PRL levels greater than 25 ng/ml; group III consisted of 17 cycles, where patients, who already developed hyperprolactinemia in a previous cycle, were treated by 3.75 mg bromocriptine daily. The serum estradiol (E2), progesterone (P) and PRL levels 1, 2, and 3 days before and at oocyte retrieval were evaluated. The E2 decrease at oocyte retrieval was significantly steeper in groups I and III. Follicular luteinization was more effective in groups I and III. The fertilization rate in groups I and III was significantly higher than in group II. High serum PRL levels seem to interfere in follicular and oocyte development. The treatment of transient hyperprolactinemia improved the patients' endocrine response and the fertilization rate of oocytes.

Metoclopramide-induced hyperprolactinaemia: effects on corpus luteum function, endometrial steroid receptor concentrations and 17 beta-hydroxysteroid dehydrogenase activity

Induced hyperprolactinaemia impairs ovarian follicular development, especially during the recruitment period. The consequences of hyperprolactinaemia during the luteal phase alone on corpus luteum function have not been characterized, nor have the actions of excessive circulating PRL on the endometrium. In this study, postovulatory 5-d administration of metoclopramide (MC) increased serum concentrations of PRL and decreased those of pregnenolone and progesterone indicating inhibition of steroidogenesis in the corpus luteum. This effect may partly explain the relatively common failure of implantation in association with induced ovulation using regimens leading to transient hyperprolactinaemia. In contrast to this, MC-induced hyperprolactinaemia during the mid-follicular (4 d) or early luteal phase of the cycle did not alter the concentrations of cytosol or nuclear oestrogen and progestin receptors or the activity of 17 beta-hydroxysteroid dehydrogenase in endometrial tissue. Thus, transiently elevated circulating PRL does not seem to have direct effects on female sex steroid receptors or their function in the proliferative or secretory endometrium.

Effects of sulpiride-induced hyperprolactinemia on human ovarian follicles during the late follicular phase

The effect of hyperprolactinemia during the midfollicular through the late follicular phase of the menstrual cycle on follicular development and follicular fluid hormone concentrations was studied. Fourteen women underwent laparotomy in the late follicular phase for gynecologic reasons; 6 were treated with sulpiride daily from the midfollicular to the late follicular phase (sulpiride group) and 8 received no treatment (control group). Daily administration of sulpiride (150 mg orally) significantly elevated serum prolactin (PRL) levels in all six women. In the small follicles (less than or equal to 8 mm in diameter), follicular fluid 17 beta-estradiol (E2) concentration was significantly lower (P less than 0.01), and testosterone (T) concentration was higher (P less than 0.05) in the sulpiride group. In the large follicles (greater than or equal to 9 mm in diameter), however, follicular fluid E2 and T concentrations showed no significant differences between the sulpiride and control groups. In the sulpiride group, the mean diameters of the follicles were significantly smaller than in the control group (P less than 0.01). These observations suggest that PRL exerts a suppressive effect on the smaller but not the larger follicles during the late follicular phase.