Which hormone is released by the hypothalamus to start the ACTH cascade in GAS?

Which hormone is released by the hypothalamus to start the ACTH cascade in GAS?

• A. CRH
• B. ADH
• C. Aldosterone
• D. Oxytocin

Answer: (A)

The sequence starts with a releasing hormone from the hypothalamus: corticotropin-releasing hormone. When the hypothalamus senses stress, it releases CRH, which travels to the anterior pituitary and stimulates the release of adrenocorticotropic hormone. ACTH then acts on the adrenal cortex to produce cortisol, helping mobilize energy and modulate the stress response. This chain—CRH from the hypothalamus triggering ACTH release and subsequently cortisol release—pins the ACTH cascade in GAS. The other substances listed have different roles: ADH regulates water balance, aldosterone is controlled mainly by the renin-angiotensin system and not initiated by the hypothalamus in this cascade, and oxytocin is involved in childbirth and lactation. Thus, corticotropin-releasing hormone is the initiator of the ACTH cascade.

The sequence starts with a releasing hormone from the hypothalamus: corticotropin-releasing hormone. When the hypothalamus senses stress, it releases CRH, which travels to the anterior pituitary and stimulates the release of adrenocorticotropic hormone. ACTH then acts on the adrenal cortex to produce cortisol, helping mobilize energy and modulate the stress response. This chain—CRH from the hypothalamus triggering ACTH release and subsequently cortisol release—pins the ACTH cascade in GAS. The other substances listed have different roles: ADH regulates water balance, aldosterone is controlled mainly by the renin-angiotensin system and not initiated by the hypothalamus in this cascade, and oxytocin is involved in childbirth and lactation. Thus, corticotropin-releasing hormone is the initiator of the ACTH cascade.