Daugeras-Bernard N, Leloup J, Lachiver F
C R Acad Hebd Seances Acad Sci D. 1976 Nov 8;283(11 D):1325-7.
Plasma thyroxine (T4) level of intact and hypophysectomized Chick embryos has been determined for the incubation interval 10 to 18 days. T4, which is the main circulating thyroid hormone, exists as early as day 10. The plasma T4 level of controls increases as power function of time from day 10 to day 17. Hypophysectomy (on day 2) produces a decrease of the plasma T4 level, but only from day 11, which accounts for the beginning of a pituitary control of the thyroid secretion after day 10.