Norris D O, Gern W A
Science. 1976 Oct 29;194(4264):525-7. doi: 10.1126/science.973134.
Thyroxine injected into the hypothalamus of neotenic Ambystoma tigrinum induces metamorphosis by activating hypothalamo-hypophysial stimulatory control of thyroid activity, thereby removing the hypothalamic block to metamorphosis.