The effect of oral administration of thyrotropin-releasing hormone on lactation

Sixteen puerperal women between the ages of 17-30 years, were studied in a double blind trial during the four weeks postpartum. Eight women received orally 20 mg of synthetic TRH three times a day, 30 minutes before the corresponding breast feeding; the remaining group received a placebo in the same fashion. The women receiving TRH exhibited higher basal concentrations of serum PRL as well as a higher increment in response to suckling; however, the PRL concentrations before and after breast feeding in this group were similar to those of the control group by the fourth week postpartum. TRH treatment showed no effect on the yield or content of milk during the four-week period. In a conjoint study, PRL concentrations did not rise after TRH administration in women with defective lactation, suggesting that some impairment of the PRL release mechanism was present. TRH caused no clinical hyperthyroidism in the mothers nor in the children. Serial determinations of serum T3 and TBG revealed values within the normal limits. It was also observed that TRH administration had no effect on FSH and LH secretion, and gonadotropin secretion was not inhibited despite of the increments on PRL concentrations. In both groups, suckling had no effect on serum levels of pituitary gonadotropins determined before and after breast feeding. We have concluded that in full lactating mothers: a) the oral administration of TRH produced a marked increment in PRL concentration but no significant augmentation of milk production was observed; b) in some cases of hypogalactia, TRH did not improve the milk production; and c) the PRL-enhanced secretion showed no effect on gonadotropin secretion.