Hormones of the Adrenal Cortex (77)
Name the 4 zones of the adrenal gland.
What is secreted by the zona glomerulosa?
What is secreted by the zona fasciculata?
What is secreted by the zona reticularis?
androgens (DHEA, androstenedione)
What is secreted by the adrenal medulla?
How does cortisol affect CRH and ACTH secretion?
decreases both; 1
Describe the relase of corticotropin releasing hormone.
During what time of day is cortisol release the greatest?
*plasma cortisol levels measured early morning; 2
Where is CRH synthesized?
paraventricular nucleus of hypothalamus
Is the half-life of CRH long or short?
What type of G protein is the CRH receptor?
What is the precursor molecule for ACTH?
pro-opiomelanocortin (POMC); 4
What type of G protein is the ACTH receptor?
What protein activates a cholesterol channel in the mitochondria, allowing it to enter and be converted into pregnenolone? In which zones does this protein act upon?
StAR; 6 (Steroidal acute regulatory protein)
What is the short-term effect of ACTH?
conversion of cholesterol into pregnenolone
Name 2 long-term effects of ACTH.
transcription of synthesis enzymes
increase in number of LDL receptors
Describe the release of ACTH.
pulsatile and diurnal
Why is aldosterone production exclusive to the zona glomerulosa?
alone possesses aldosterone synthase
Name a hormone and ion that increase StAR in the zona glomerulosa.
What type of G protein is the angiotensin 2 receptor in the zona glomerulosa?
How does high extracellular K+ affect synthesis and release of aldosterone?
increases synthesis and release of aldosterone; 8
How does aldosterone affect sodium, water, and K+ reabsorption/secretion?
Which parts of the nephron are affected by aldosterone?
principal cell of DCT/collecting duct
Name 3 channels in the principle cells of the distal convoluted tubule/collecting duct that are enhanced by aldosterone.
K+ (ROMK) channels; 10
How does the body prevent cortisol from exerting a large mineralcorticoid effect?
11-beta-hydroxysteroid dehydrogenase converts cortisol into cortisone
Name a herb that blocks the enzyme 11-beta-hydroxysteroid dehydrogenase.
How can licorice affect sodium retention?
increase sodium retention, leading to hypertension--"Mineralcorticoid excess syndrome"
How does aldosterone secretion affect angiotensin 2 release?
negative feedback; 11
Explain how compensatory mechanisms in congestive heart failure can exacerbate the disease.
Name a cause of hypersecretion of aldosterone.
Conn's syndrome due to glomerulosa tumor
Describe K+, renin levels, and blood pressure in Conn's syndrome.
low renin levels
increased blood pressure
Conn's syndrome Rx
aldosterone antagonists and surgical resection
Describe hydration, blood pressure, [Na], and [K] in hyposecretion of aldosterone.
hypotension (marked postural hypotension due to low blood volume)
Describe blood aldosterone, renin, and angiotensin 2 in hyposecretion of aldosterone.
increased angiotensin 2
Name the disorder: autoimmune disorder affecting the whole adrenal cortex.
During what time of day is release of cortisol the greatest?
Name the plasma protein bound to cortisol in the blood.
cortisol binding globulin (transcortin)
Where in/on the cell are cortisol receptors found?
inside the cytoplasm. 13
Review actions of glucocorticoids.
How does cortisol affect insulin?
decreases effects of insulin on glucose uptake
How does cortisol affect protein metabolism?
increases proteolysis in all cells (except the liver)
How does cortisol affect fat metabolism?
increases lipolysis and mobilizes fatty acids
How does cortisol affect the immune system and inflammation?
How does cortisol affect lysosomes?
stabilizes lysosomal membranes to prevent release of proteolytic enzymes
How does cortisol affect capillary permeability and tissue edema?
How does cortisol affect synthesis of PGs and leukotrienes?
decreases both by decreasing phospholipase A2
Review anti-inflammatory/immunosuppressant effects of cortisol.
Review effects of cortisol on PGs and leukotrienes.
How does cortisol affect response to NE and angiotensin 2?
What hormone is administered prior to premature births? Explain.
increases surfactant production
Review actions of cortisol.
How does excess cortisol affect connective tissue?
loss of collagen and connective tissue
Describe 3 ways in which excess cortisol affects bone.
decreases formation and increases resorption
increases PTH and Calcitrol on bone (increased resorption)
How does excess cortisol affect Ca metabolism?
decreases absorption from GIT
increases excretion by kidneys
*negative Ca balance
Name 4 causes of hypersecretion of cortisol.
What is the difference between Cushing's disease and syndrome?
Cushing's disease refers to increase release of ACTH from pituitary
Describe plasma ACTH and cortisol in Cushing's disease.
Describe plasma ACTH and cortisol in Cushing's syndrome.
low ACTH (negative feedback)
Review manifestations of hypercortisolism.
What happens to the HPA axis of someone on chronic steroid therapy?
adrenal cortex atrophies because cortisol suppresses CRH and ACTH
Name 3 causes of primary adrenal insufficiency.
Describe a situation in which secondary adrenal insufficiency results.
sudden withdrawal of glucocorticoids after prolonged therapeutic use
Review clinical features of Addison's disease.
Describe blood pressure, [Na] and [K] in Addison's disease.
Describe ACTH levels in Addison's disease.
Addison's disease Rx
replacement therapy with cortisol and a mineralcorticoid
Is cortisol or aldosterone production more affected in secondary adrenal insufficiency?
ACTH has less effects on integrity of zona glomerulosa
What is the major androgen secreted by the adrenal cortex?
What is the commonest enzyme deficiency causing hyposecretion of adrenal cortex hormones?
Explain how low cortisol and low aldosterone can cause salt-losing virilizing congenital adrenal hyperplasia.
Salt-losing virilizing congenital adrenal hyperplasia Rx
reduce ACTH levels by giving glucocorticoid; 22