T1 L6 adrenal cortex hormones & physiology

Question 1

anatomy of adrenal cortex

Answer 1

90% outer cortex: GFR stress, sodium, glucose homeostasis, sex androgens
10% inner medulla: stress response

Question 2

cortex

Answer 2

synthesis of many hormones w/ similar chemical structure (steroid hormones)
- derived from cholesterol (lipid solube and orally active)

Question 3

3 divisions of adrenal cortex

Answer 3

cells w/I different areas possess different enzymes therefore synthesise different adrenocortical hormones

1. Zona Glomerulosa
2. zona fasiculata
3. zona Reticularis

Question 4

steroid hormones- variety of effects, usually classified according to predominant action (2 classifications)

Answer 4

1. Glucocorticoids: cortisol bgl

2. mineralocorticoids : aldosterone Na+

Question 5

synthesis of hormones from cholesterol

Answer 5

cholesterol –> progesterone –> aldosterone and cortisol

cholesterol –> testosterone

Question 6

zona glomerulosa

Answer 6

18- hydroxylase enzyme, aldosterone synthesis

Question 7

zona fasiculata & zona reticularis

Answer 7

17a hydroxylase
17a hydroxypregenolone, 17a hydroxyprogesterone + hormones derived from these
-CORTISOL (synthesised in zona fasiculata)
- ANDROGENS (synthesised in zona reticularis)

Question 8

production o sex hormones in adrenal cortex

Answer 8

testosterone (m) and oestradiols (f) are only significant in adrenal disorders

Question 9

control of glucocorticoid secretion

Answer 9

hypothalamus CRH –> Ant pituitary gland ACTH –> adrenal cortex CORTISOL (-ve feedback on CRH)
diurnal rhythms 9:00 max, 4:00 min

Question 10

secretions of ACTH

Answer 10

pulsatile

• peak at time of waking-
• nadir in middle of night
• ^ secretion at times of prolonged stress

Question 11

Cortisol diurnal rhythm

Answer 11

same pattern as ACTH but 2 hrs after

- sleep wake ( disrupted by shift work & long haul travel)

Question 12

transport of glucocorticoids

Answer 12

Lipid soluble
-10% cortisol free & active
- 90% bound to plasma proteins (inactive), same proteins transport other glucocorticoids + progesterone
( 75% transcortin/CBG corticosteroid binding globulin
- 15% albumin)

Question 13

pregnancy

Answer 13

Ass. w/ ^ CBG: compensatory ^ in circulating plasma cortisol concentration (protein bound)
- amount of free cortisol remains stable

Question 14

Metabolism of adrenal steroids

Answer 14

• mainly in liver: here it is GLUCURONIDATED to form water soluble forms which are excreted in urine
  glucuronidated: bound to glucose to make water soluble

Question 15

cellular effects of steroids and glucocorticoids

Answer 15

• action on intracellular rs: alteration of gene expression results in delay (hrs/days)
• effects of cortisol can be rapid (e.g. feedback inhibition of ACTH secretion)

Question 16

Cortisol

Answer 16

normal physiological concs, most important actions of CARB METABOLISM
-opposite to insulin: antagonises effects of insulin on cellular uptake of glucose, stim glycogenolysis,stim hepatic gluconeogenesis
- in excessive concs cortisol causes fat synth & deposition in novel anatomical sites:
face trunk & intrascapular region of shoulder (backpack), excess glucose stored as fat
- in liver: cortisol stim a.acid uptake (enhanced gluconeogenesis)
- in periphery: inhibits a.acid uptake and protein synthesis => net loss of skeletal muscle mass
- glucocorticoids stimulate aldosterone rs although aldosterone sensitive tissues have enzyme that converts cortisol (active) –> cortisone (inactive)

Question 17

more effects of excess cortisol

Answer 17

• enhanced vasoconstrictor response to catecholamines => ^ BP
• phsychological effects: elation and sedation