Adrenal Hormones Flashcards
What does the cortex of the adrenal cortex do?
-secretes corticosteroids
How are corticosteroids made?
- synthesized from cholesterl -> provided mostly by LDLs in the plasma
- most attach to coated pits
- ACTH increases number of LDL receptors
- cholesterol converted to pregnenolone in mitochondria
- enzyme for conversion = cholesterol desmolase (RATE LIMITING STEP)
- both ACTH and angiotensin II increase the conversion of cholesterol to pregnenolone
What are the corticosteroids?
- progesterone
- deoxycorticosterone
- aldosterone
- cortisol
What is the major mineralocorticoid?
Aldosterone
How do mineralocorticoids affect electrolytes?
- increases Na reabsorption by kidney tubules -> principal cells in distal tubule
- hyperkalemia increases aldosterone
- increases K secretion by kidneys -> principal cells in distal tubule
- increases H+ secretion by kidneys -> intercalated cells in distal tubules
- secretion is controlled by angiotensin II and K+
What secretes mineralocorticoids?
-zona glomerulosa
What is the major glucocorticoid?
-cortisol -> essential in stress response
What is the secretion of glucocorticoids controlled by?
-secretion controlled mainly by ACTH
+uporegulates its own receptor
+under the influence of CRH
+second messenger for both CRH and ACTH is cAMP
What secrets glucocorticoids?
-zona fasciculata
What does cortisol have a negative feedback response on?
-CRH and ACTH
How is cortisol regulated with the circadian rhythm?
- highest cortisol levels before waking
- lowest in the evening
What are androgen if hormones?
-19 carbon steroids that are precursors to the estrogens
+DHEA and androstenedione
+DHEA is converted to testosterone in the testes
Adrenal androgens are. Excreted. As ______________ in the urine.
17-ketosteroids
How do 18 carbons steroids have estrogen in activity?
-oxidation of one of the rings occurs in the ovaries to produce estrogens, but not in the adrenal glands or testes
What secretes androgens can hormones?
-zona reticularis
What happens when there is a lack of aldosterone in the body?
- total loss causes death in days unless extensive salt therapy and mineralocorticoid injections are available
- w/o mineralocorticoids K levels in ECF rise and Na and Cl are lost rapidly from urine
- total ECF and blood volume become greatly reduced
- person develops diminished cardiac output and progresses to a shock like state
- hyperkalemia and serious cardiac toxicity
What happens when there is an excess of aldosterone?
- increase in ECF and arterial pressure
- small effect on plasma Na conc -> Na absorption in renal tubules is accompanied by equivalent amount of water reabsorption
- hypokalemia and muscle weakness
- stimulates transport of K from ECF into most cells of the body
- causes alkalosis (H+ secreted in exchange for Na+)
Overall effect of aldosterone.
-increases renal tubular reabsorption of Na and increases K in the urine
Cellular sequence of events leading to Na reabsorption.
- Aldosterone is lipid soluble and diffuse readily into the interior of the tubular epithelial cells
- Aldosterone combines with mineralocorticoid receptor proteins
- Aldosterone receptor complex diffuses into nucleus
- RNA transcription is induced
- Na-K ATPase pump proteins are among those formed as a result of this induction
- Epithelial sodium channel is also formed
How is aldosterone regulated?
- almost entirely independent of the regulation of cortisol secretion
- increased K conc greatly increases aldosterone secretion
- increased angiotensin II conc greatly increases aldosterone secretion
- ACTH necessary for aldosterone secretion but has little effect in controlling rate of secretion
What are the functions of glucocorticoids?
- stimulates gluconeogenesis -> may lead to adrenal diabetes
- resists stress
- resists inflammation
- causes resolution of inflammation
- inhibits immune response
- maintains vascular response to catecholamines
How do glucocorticoids stimulate gluconeogenesis?
- increases protein catabolism
- mobilizes aas from extra hepatic tissues
- enhances transport of aas into hepatic cells
- increases enzymes requires to convert aas to glucose
- decreases glucose utilization by cells
- increases lipolysis
How can glucocorticoids resist inflammation?
- induces synthesis of lipocortin which inhibits phospholipase
- inhibits production of interleukin-2
- inhibits release of histamine and serotonin
- blocks inflammatory response to allergic reaction
- decreases number of eosinophils and lymphocytes in blood
What are the primary and secondary reasons for hypoadrenalism/ Addison’s disease?
Primary: due to injury to adrenal cortex
Secondary: due to impaired function of pituitary gland
