Perinatal thiouracil exposure depresses corticotropin-releasing factor activity in 15 day old rats.

Although previous in vivo studies have shown thiouracil to delay maturation of the hypothalamus-pituitary-adrenal (HPA) axis response to stress, the nature of the developmental deficit was not determined. By in vitro methods we determined which HPA components are influenced by thiouracil-induced hypothyroidism in 15 day old rats. Our results indicate that adrenal response to ACTH stimulation and adenohypophysial ACTH content were not significantly modified by thiouracil exposure. On the other hand, the corticotropin-releasing factor-like activity of median eminence extracts was severely depressed by thiouracil-induced hypothyroidism. Thus, the delayed maturation of functional capacity of the central nervous system caused by hypothyroidism includes synthesis of biologically active corticotropin-releasing factor.