Interaction of thyrotropin (TSH) and gonadotropins in the function of genital organs. Effect of TSH and gonadotropin pretreatment (hormonal imprinting) of newborn rats on hormonal overlap in adult animals.

At the age of 25 days the TSH-gonadotropin overlap is minimal in rats and extremely high doses of TSH are required to produce gonadotropin-like responses. Although the effect may be due also to some occasional contamination, nevertheless a single treatment of newborn animals (hormonal imprinting) with either hormone augmented the response to a second treatment with either hormone performed at 25 days of age. Newborn rats pretreated with either TSH or gonadotropin were exposed to a second TSH challenge at the age of 25 days exhibited responses which were not commeasurable to those observed after gonadotropin treatment alone. However, the amplifying action of TSH pretreatment with regard to the second response to gonadotropin was comparable or even more apparent than that of gonadotropin pretreatment.