Adrenal Physiology

Question 1

Name the three layers of the adrenals and the respective hormones produced:

Answer 1

Zona glomerulosa (cortex) - aldosterone
Zona fasiculata (cortex) - cortisol
Zona reticularis (medulla) - androgens

Question 2

Whats the role of steroidogenic acute regulatory protein ?

Answer 2

a pore that allows cholesterol to access the inner mitochondrial membrane where steroid synthesis occurs

Question 3

Which enzyme converts testosterone to estradiol (E2)?

Answer 3

aromatase

Question 4

True or false: cortisol release is diurnal

Answer 4

False: pulsatile (10 times a day)

Question 5

What’s the diurnal fluctuation of cortisol?

Answer 5

highest in the morning 6-10 am and lowest at midnight

Question 6

Stress impact which centres?

Answer 6

hypothalamic which release CRH

Question 7

Increased cortisol inhibits what?

Answer 7

ACTH and CRH release inhibited (negative feedback)

Question 8

What forms of cortisol are in circulation?

Answer 8

75% is bound to cortisol binding globin (CBG)
20% is bound to albumin
4-5% is free

Question 9

True or False: cortisol goes into the nucleus for transcriptional regulation

Answer 9

true

Question 10

What are the effects of cortisol on glucose?

Answer 10

• causes liver to synthesize glucose (gluconeogenesis)
• stimulates hepatic glycogen storage
• decreases peripheral glucose utilization
• increases blood glucose making glucose available for insulin insensitive tissues (tissues that don’t require insulin for glucose uptake: brain, heart, kidney, red blood cells)
• stimulates breakdown of proteins to amino acids
• stimulates lipolysis

Question 11

What effect does cortisol have on mineral?

Answer 11

• electrolyte/H2O balance (high cortisol has an effect on mineralocorticoid receptors: salt and water retention)
• antagonizes actions of Vitamin D and impairs calcium absorption

Question 12

What is the effect of cortisol on the immune system?

Answer 12

• immunosuppression (↓lymphocyte infiltration, ↓lymphocyte numbers, suppress cell-mediated hypersensitivity, impairs phagocytes)
• decreases inflammation

Question 13

What is the effect of cortisol on CV?

Answer 13

maintains integrity of CV system (↓permeability of capillary endothelium, inotropic action on myocardium, facilitates vasoconstriction)

Question 14

What are the effects of aldosterone?

Answer 14

• Increased renal tubular resorption of sodium: sodium loss in urine is decreased
• Increased resorption of water, with consequent expansion of extracellular fluid volume. This is an osmotic effect directly related to increased resorption of sodium
• Increased renal excretion of potassium

Question 15

What are the genetic effects of aldosterone?

Answer 15

Aldosterone stimulates transcription of the gene coding for the sodium-potassium ATPase, leading to increased numbers of sodium pumps in the basolateral membranes of distal tubular epithelial cells.

Aldosterone also stimulates expression of a sodium channel which facilitates uptake of sodium from the tubular lumen.

Aldosterone has effects on sweat glands, salivary glands and the colon which are essentially identical to those seen in the distal tubule of the kidney.

Question 16

Besides ACTH, what causes the release of aldosterone from the adrenal cortex?

Answer 16

As a response to low ECF volume (ie. less blood coming to renals) and low Na+ (smaller stimulus), Renin from juxtaglomerular apparatus from kidneys convert Angiotensinogen to angiotensin 1 and 2 –> an-2 activates adrenals

High K+ (small increases in K+) directly activates adrenals

Question 17

What factors suppress aldosterone?

Answer 17

Factors which suppress aldosterone secretion include high serum sodium, low serum potassium and atrial natriuretic peptide

Question 18

what is the rate-limiting step for catecholamine synthesis?

Answer 18

tyrosine hydroxylase

Question 19

what are the actions of catecholamine on cardiac system?

Answer 19

increases heart rate
increases contractility
therefore increases cardiac output
increases dromotropy (cardiac conduction)
increases blood pressure
redistributes blood flow from gut, kidney, skin to heart, brain, skeletal muscle

Question 20

what are the actions of catecholamine on smooth muscle?

Answer 20

pupil dilation
bronchodilation
decreased gut motility

Question 21

what are the actions of catecholamine on metabolism?

Answer 21

glycogenolysis
gluconeogenesis
lipolysis

Question 22

T or F: adrenal androgens are an importance source for males

Answer 22

False:

in women, can be a major source of androgens and lead to hirsutism and abnormal menses