Maternal—Fetal Endocrine Interrelations: Demonstration of TSH Release from the Fetal Hypophysis in Pregnant Rats Administered Synthetic TRH 1

Abstract

Summary

Synthetic TRH (L-(pyro)-Glu-L-His-L-Pro-NH₂), administered to the pregnant rat on the last day of gestation, stimulates release of TSH from the fetal hypophysis, as evidenced by a 3-fold elevation of plasma TSH level and significant change in the ratios of thyroid and blood radioactivity of the newborn. The stimulatory effect of TRH on the in vitro release of TSH from the postnatal pituitary of rats 1-20 days old was also demonstrated. The capacity of the perinatal pituitary to respond to TRH suggests that functional maturation of the hypothalamo—hypophysial—thyroid system may occur in this period.