Hypothalamic-Pituitary-Adrenal Axis Flashcards
What 6 things does the hypothalamus regulate? How does it do this?
- maintenance of homeostasis
- reproduction
- metabolism
- eating and drinking behavior
- energy utilization
- osmolarity and blood pressure
secretes hormones via the pituitary
What is the hypothalamic-pituitary-adrenal axis?
- hypothalamus secretes CRH to stimulate the anterior pituitary
- in response, anterior pituitary secretes ACTH, which stimulate cortisol metabolism and secretion from the adrenals
- increased cortisol in the bloodstream acts a negative feedback loop, which decreases CRH and ACTH production
What are the 3 zones of the adrenal cortex? What hormones do they secrete?
- zona glomerulosa - mineralocorticoids - aldosterone (SALT)
- zona fasciculata - glucocorticoids - cortisol, corticosterone (SUGAR)
- zona reticularis - sex hormones - androgens, estrogen (SEX)
What hormones are secreted by the adrenal medulla?
catecholamines - epinephrine, norepinephrine
What is responsible for cortisol release from the adrenal glands? What are 4 of its roles?
ACTH stimulation from the anterior pituitary
- regulates macronutrient metabolism
- maintain GI structure and function
- maintain normal BP
- stress adaptation - trauma, surgery, illness, pain, inflammation
What is responsible for aldosterone release from the adrenal glands? What are 2 of its roles?
RAAS - increased serum K = increased aldosterone, decreased serum K = decreased aldosterone
- increases ECF Na+ and H2O concentration
- decreases ECF K+ concentration
What is responsible for catecholamine release from the adrenal medulla? What are 5 of their roles?
stress, pain, injury, SNS stimulation = norepinephrine and epinephrine release
FIGHT OR FLIGHT
- vasoconstriction
- increased HR and contractility
- vasodilation of smooth muscles (beta-stimulation)
- glycogenolysis and gluconeogenesis to increase glucose availability
- lipolysis, increased metabolic rate
What are the likely results of pituitary tumors, adrenal cortical tumors, and adrenal medullar tumors?
increased ACTH = increased cortisol (Cushings)
increased cortisol (Cushing) and aldosterone (cats) secretion
(pheochromocytoma) excess and episodic release of catecholamines
What is primary and secondary hypoadrenocorticism? How are they different?
non-functional pituitary gland = decreased cortisol, normal aldosterone = normal electrolytes
destruction of the zona glomerulosa and fasciculata = decreased cortisol and aldosterone = cortisol and mineralocorticoid deficiency (most common, dogs)
What is the normal axis associated with growth hormone production? What are 3 aspects to its negative feedback loop?
- hypothalamus secretes GHRG, which stimulates the anterior pituitary gland
- in response, the pituitary gland secretes GH
- GH induced the liver to produce IGF-1
- increased IGF-1 stops the production of GH from the pituitary and GHRH
- increased GH self-regulates and decreases GHRH
- somatostatin from the hypothalamus blocks this pathway
What are 4 functions of growth hormone?
- insulin antagonism
- lipolysis
- protein synthesis
- epiphyseal growth
What are 4 functions of IGF-1?
- insulin-like activity
- antilipolytic activity
- protein synthesis
- epiphyseal growth
What is acromegaly?
pituitary tumor results in secretion of GH and increase in IGF-1 from the liver
What hormones are produced by the posterior pituitary?
- ADH
- oxytocin