Growth Hormone-Releasing Activity in the Hypothalamus of Primates

Growth hormone (GH)-releasing activity of simian and human hypothalamus was investigated by the method of in vivo depletion of growth hormone content of rat pituitaries. The extracts of the stalk-median eminence (SME) region prepared from 6- to 8-month-old rhesus monkeys and from a 3-year-old child were injected into the carotid artery of 30-day-old recipient rats. The pituitaries of the recipient animals were assayed for GH content by the “tibia test” method. Rhesus monkey SME extracts induced in the recipient rats a depletion of growth hormone pituitary content of about 70 %. Human SME extract caused a depletion of GH content of about 50 %. Comparable cerebral cortex extracts of simian and human origin had no effect on pituitary GH content. These findings indicate that a growth hormone-releasing activity is present in the hypothalamus of primates. (Endocrinology79: 448, 1966)