Effect of metoclopramide on maternal and fetal hyperprolactinemia

Serum prolactin concentration in normal and small for gestational age fetuses

OBJECTIVES

To study fetal and maternal serum prolactin concentrations in appropriately-grown (AGA) fetuses and in small for gestational age (SGA) fetuses.

DESIGN

A cross-sectional study of 27 AGA and 27 SGA fetuses undergoing cordocentesis for prenatal diagnosis or for determination of fetal karyotype and acid-base balance. Serum prolactin concentration was measured by radioimmunoassay.

SETTING

Harris Birthright Research Centre for Fetal Medicine.

RESULTS

In the AGA group, both fetal and maternal serum prolactin concentration increased significantly with gestation (P < 0.001 and P < 0.01, respectively). In the SGA group, the fetal concentration of prolactin was significantly higher (P < 0.05), but the maternal serum prolactin concentration was not different from that of the AGA group.

CONCLUSIONS

The finding of prolactin in the fetal circulation suggests that the anterior lobe of the pituitary is functioning from at least 12 weeks gestation. The increased serum prolactin concentration in SGA fetuses may be the consequence of hypoglycemic stress on the pituitary or the relative immaturity of the inhibitory hypothalamic-pituitary pathways.

Effect of cimetidine on maternal and fetal prolactin secretion during labor

Cimetidine, an H2 receptor antagonist, is a potent stimulant of PRL secretion in normal women. In the present study, the PRL response to cimetidine was studied in 34 normal pregnant women and their fetuses during labor. Serum maternal PRL levels increased significantly after the acute iv injection of 400 mg cimetidine 30-45 min before delivery (10 women) as compared to 7 control women given saline. However, PRL levels in serum of umbilical vein and artery did not increase. Similar results concerning PRL levels in umbilical vein and artery serum were obtained when cimetidine was injected 10-20 min (8 women), 60-75 min (8 women) and 90-120 min (8 women) before delivery. It is suggested that fetal pituitary lactotrops are not responsive to cimetidine stimulation.

Absent prolactin (PRL) response to thyrotropin releasing hormone (TRH) and somatostatin (SRIF) in at term fetus

To study the effect of thyrotropin-releasing hormone (TRH) and somatostatin (SRIF) on prolactin (PRL) secretion in at term human fetus these peptides have been administered to at term pregnant women during labor. Evidence has been reported that TRH and SRIF cross the placental barrier and affect the secretion of pituitary hormones. 400 micrograms TRH were administered to 37 pregnant women. As control 11 women received saline. In cord blood (CB) of neonates whose mothers received TRH CB PRL concentration was not different from those treated with saline, with values ranging between 192 +/- 18 and 342 +/- 48 ng/ml. 500 micrograms cyclic SRIF diluted in saline was infused over a period of 30 min in 55 women. Control subjects were infused with saline. At birth CB PRL concentration in SRIF treated neonates ranged between 266 +/- 32 and 327 +/- 48 ng/ml. In neonates whose mothers were treated with saline, CB PRL was 305 +/- 31 ng/ml. This value was not significantly different from that in SRIF-treated groups. Our findings suggest that in at term human fetus TRH does not stimulate PRL secretion probably because fetal pituitary secretes PRL at maximal releasing activity. Furthermore SRIF administration does not have any effect on fetal PRL secretion as consistently observed in adults.