C. W. Asling

ANTERIOR PITUITARY REGULATION OF SKELETAL DEVELOPMENT

Publisher Summary This chapter describes the roles of the pituitary and thyroid glands in controlling skeletal development of the rat. Growth of the skeleton is retarded following hypophysectomy or thyroidectomy. The extent of the retardation is dependent upon the age at the time of operation. The most marked dwarfism follows hypophysectomy of young rats, although the retardation develops slowly than after hypophysectomy of older rats. This suggests that the earliest postnatal growth is relatively less dependent on pituitary hormones. The skeletal growth can be restored to normal in hypophysectomized rats by administering growth hormone in adequate amounts. No other hormone tested possesses this ability. Maturation of the skeleton is also retarded by hypophysectomy or thyroidectomy. The extent of retardation is independent of the age at the time of operation. The equivalent of 2–3 weeks of further differentiation follows hypophysectomy or thyroidectomy of immature rats at whatever age. The maturation can be restored to normal by administration of thyroid hormone. In thyroidectomized rats, this hormone also stimulates growth through its action on restoring pituitary function. Growth hormone is without effect on skeletal maturation.