THYROID-FUNCTION IN EMBRYONIC AND PERINATAL JAPANESE QUAIL

Thyroid function in Japanese quail embryos is similar to that of domestic fowl embryos, suggesting the existence of a common patter of thyroid development in precocial birds, regardless of differences in body size. From 10-15 days of incubation there are steady increases in the capacity for hormone production and release, but circulating triiodothyronine (T3) and thyroxine (T4) concentrations are low. During the perinatal period hormone secretion rises sharply. Serum concentrations of both T3 and T4 are significantly higher in embryos that have penetrated the chorioallantoic membrane that in ones that have not. Thus high thyroid hormone concentrations are associated with the beginning of pulmonary respiration and the high metabolic demands of the hatching process.