Which function serves as an inhibiting factor for somatotropin release?

Which function serves as an inhibiting factor for somatotropin release?

• A. Gonadotropin-releasing hormone
• B. Growth hormone-releasing hormone
• C. Somatomedin
• D. Somatostatin

Answer: (D)

Growth hormone release is controlled by two hypothalamic signals: a stimulatory one and an inhibitory one. The stimulatory signal, GHRH, prompts the anterior pituitary to release growth hormone. The direct inhibitory signal is somatostatin, which dampens or stops secretion from the pituitary. So, when a question asks for what inhibits somatotropin release, somatostatin is the right answer because it directly suppresses GH secretion. Although somatomedin (IGF-1) can feed back to reduce GH production indirectly by lowering GHRH and increasing somatostatin, the immediate inhibitory factor is somatostatin. GnRH controls gonadotropins, not growth hormone, so it doesn’t fit.

Growth hormone release is controlled by two hypothalamic signals: a stimulatory one and an inhibitory one. The stimulatory signal, GHRH, prompts the anterior pituitary to release growth hormone. The direct inhibitory signal is somatostatin, which dampens or stops secretion from the pituitary. So, when a question asks for what inhibits somatotropin release, somatostatin is the right answer because it directly suppresses GH secretion. Although somatomedin (IGF-1) can feed back to reduce GH production indirectly by lowering GHRH and increasing somatostatin, the immediate inhibitory factor is somatostatin. GnRH controls gonadotropins, not growth hormone, so it doesn’t fit.