Human lactational response to oral thyrotropin releasing hormone

Abstract

Several studies were designed to evaluate the effect of oral TRH on prolactin (PRL) secretion and mammary function in nursing women. Initially, efficacy was studied in nursing women following 5 mg TRH. PRL levels rose to a mean maximum of 46.3 ng/ml above baseline at 60 min. Plasma TSH also incresed from a mean baseline of 2.6 to 17.6 muU/ml at 180 min. No changes were observed following placebo. In order to observe the long term effects of oral TRH, two groups of women in full nursing were studied. Beginning on day 29 postpartum, either 5 mg TRH or placebo were taken twice daily for four weeks. No chronic elevations were observed in maternal PRL and TSH or in infant TSH before or after one month of either regimen. Milk composition expressed in terms of per cent protein and per cent fat did not differ between the groups. Weekly gonadotropin levels were also similar as were infant weight gain and growth. In a group of women with lactational insufficiency receiving 5-20 mg TRH twice daily for five days, basal PRL concentrations markedly increased. While changes in milk composition were not significant, fat percentages increased slightly and protein percentages declined. Breast engorgement and milk letdown increased and full nursing was restored. While the oral TRH used in fully nursing women had no demonstrable effect on mammary function, it may prove useful in those women with lactational insufficiency. Because two women developed iatrogenic hyperthyroidism following 40 mg oral TRH twice daily, care must be exercised in determining the dosage to be employed.