FSH-TSH functional overlap in cockerel testicle. Durable amplification of the hormone receptors by treatment at hatching.

Functional overlap of FSH and TSH in cockerel testicle is expressed by alteration of testicular weight and canalicular diameter length. While on neonatal exposure TSH was more active than FSH, at five weeks of age both hormones developed an equal action. A single neonatal exposure to FSH had a durable effect on testicle weight and canalicular diameter, while the effect of post-hatching TSH persisted only in respect of the second parameter. A single neonatal exposure to TSH failed to amplify TSH effect on a second exposure at five weeks of age, while neonatal TSH and FSH treat equally enhanced the effect of FSH given at five weeks. This suggests that under given conditions, perinatal hormone excess may account for lasting amplification of the receptor(s) not only in respect of the adequate hormone, but also in respect of a related hormone, hormone-like material or analogon.