GROWTH HORMONE CONTENT AND METABOLIC ACTIONS OF HUMAN PITUITARY GLANDS1,2

Abstract

Saline suspensions of human pituitary removed at autopsy produced the typical metabolic effects attributed to purified growth hormone of beef and hog origin, when injected into hypophysectomized rats. These effects included, in addition to growth promotion, the maintenance of skeletal and cardiac muscle glycogen on fasting, and an increase in the plasma inorganic phosphate level. Assays of single pituitaries revealed that approximately 100/[mu]g of wet pituitary tissue contained one growth-promoting unit (the daily dose that induces a daily weight increment of 1 g in hypophysectomized rats). The growth hormone content of pituitaries from adults over 45 years of age did not differ significantly from that of a 12-year old boy or an 8-month fetus, and the pituitaries removed from these older adults were metabolically active when injected into rats. These observations suggest, (a) that cessation of growth in a man is not due to a deficiency of growth hormone, but to a change in the responsiveness of the target cells, and (b) that the actions of endo- genous growth hormones in animals and man are similar.