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Endocrine system anatomy and physiology
Hunger and satiety
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adrenal cortex regulation of p. 332
adrenal insufficiency and p. 355
in Cushing syndrome p. 221, 354
secretion of p. 339
signaling pathways of p. 353
Adrenocorticotropic hormone, also known as adrenocorticotropin, corticotropin, or simply ACTH, is a peptide hormone that helps regulate the release of hormones by the adrenal glands which sit above the kidneys. Secretion of ACTH is dependent on the hypothalamic-pituitary axis.
The hypothalamus, which is at the base of the brain, secretes corticotropin releasing hormone, or CRH, into the hypophyseal portal system - which is a network of capillaries linking the hypothalamus to the anterior part of the pituitary gland.
In the anterior pituitary, there are many different types of cells, each responsible for producing a type of hormone.
The corticotropin releasing hormone binds to a surface protein of one of these cell types, called corticotroph cells, and stimulates them to release ACTH.
Inside corticotroph cells, ACTH is synthesized from a large precursor molecule called pre- proopiomelanocortin, or pre- POMC.
Pre- proopiomelanocortin has a short tail called a leader or signal peptide which is cleaved off to form proopiomelanocortin, or POMC, and POMC is then split into multiple peptide hormones, and one of them is ACTH.
ACTH is then stored inside granules within the corticotroph cells, where it waits until it’s released into the blood.
Normally, ACTH is released in a pulsatile manner throughout the day and peaks in the morning around 6am but it is also secreted in response to various forms of stressful stimuli.
Adrenocorticotropic hormone is responsible for regulating many bodily functions, including stress response, energy balance, carbohydrate metabolism, and immune system activity. Too much or too little ACTH can have serious consequences for overall health.
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