Increase of Serum Thyrotropin (TSH) of Suckling Rats after Thyroliberin (TRH) Injection to Lactating Mothers

Abstract

Injection of 50 μg TRH to lactating rats 15 days after parturition was followed 4h after treatment by an increase of serum TSH and a decrease of absolute and relative pituitary TSH content in suckling pups when compared to sucklings of saline-treated mothers. The weight of the pituitary and thyroid also decreased. Results indicate that TRH administered to lactating rats induces release of TSH from the pituitary of suckling pups. An increase of the variability of serum TSH and a decrease of pituitary TSH content at noon in pups of saline-treated mothers suggest the presence of diurnal variation of TSH secretion in 15-day-old rats.

Review Hormones in Milk

“…According to Amarant et al (45), the concentration of TRH in milk exceeds that in serum. Their suggestion that milk might be a source of TRH in suckling rats is supported by (a) limited decrease of TRH serum levels and presence of TRH in the upper gastrointestinal tract of suckling rats after pancreatectomy (50); (b) the disappearance of contractile response to TRH in the duodenum of suckling rats after weaning whereas continuation of suckling can prevent its disappearance (51); and (c) interesting studies of the Bratislava group (52). They have shown that injection of TRH (50 p.g) to lactating rats 15 days after parturition is followed shortly (4 h) by an increase of serum thyroid-stimulating hormone (TSH) and a decrease of pituitary content in suckling rats when compared to sucklings of saline-treated mothers.…”