Influence of corticotropinreleasing factor on the in vitro thyroxine and thyrotropin secretion in newly hatched fowl.

Injections of ovine corticotropin-releasing factor (oCRF) are known to increase circulating thyroid hormone levels in the chicken embryo (MEEUWIS et al., 1989). This can in part be explained by a direct effect of the hypothalamic hormone on the thyroid gland and/or the stimulation of the thyrotropin (TSH) release from the pituitary. We tested these two assumptions in two separate perifusion experiments. Our results clearly indicate that oCRF does not influence the in vitro thyroxine (T-4) secretion from the thyroid. The pituitaries of the newly hatched chickens, however, released significant amounts of TSH after in vitro treatment with oCRF. Growth hormone and luteinizing hormone secretions were also elevated after the oCRF stimulation period, but this release was less pronounced compared to the TSH release. As a conclusion we postulate that oCRF mediates its effect on the thyroidal status of the chicken through stimulation of TSH release and not through a direct effect on the thyroid.