Adrenal Flashcards
(40 cards)
What is the precursor of all steroid hormones?
Cholesterol
What 2 things facilitate the formation of pregnenolone and progesterone (precursors for cortisol and sex steroids) from cholesterol?
1) Angiotensin II
2) ACTH
How is cortisol production limited to the zona fasciculata and reticularis?
17-hydroxylase (enzyme for cortisol synthesis) is only located in the zona fasciculata and reticularis (not in glomerulosa)
How is aldosterone secretion regulated?
1a) ↓BP detected by Macula Densa → paracrine signalling to JG cells → renin
b) Renin convert Angiotensinogen (liver) to AT1
c) ACE convert AT1 to AT2 in lungs
d) AT2 lead to production of aldosterone in adrenal medulla
2) High K+
3) ACTH
What are the 2 renal actions of aldosterone?
1) ↑ Na retention in collecting ducts → ↑ECF voliume
2) ↑K+ secretion → ↓K+ conc.
Would hypovolemia cause K+ loss physiologically?
No
- hypovolemia along actives RAAS but AT2 inhibits K+ channels (ROMK)
whereas in hyperK+
- renin is inhibited → ↓inhibition of K+ channels
- but activation of aldosterone by high K+
How does one assess if there is an issue with aldosterone production?
Measure aldosterone:renin ratio
What are 4 biological effects of cortisol?
1) Survival during stress
2) Vascular reactivity to catecholamine
3) Intermediary metabolism
4) Immune suppression
5) Anti-inflammatory effect
How is cortisol secretion regulated?
Hypothalamus → CRH
Pituitary → ACTH
Adrenal cortex → Cortisol
1) -ve feedback of cortisol on pituitary and hypothalamus
2) Stress and diurnal rhythm (high in morning, low at night)
What are 2 causes of adrenal failure/Addison’s disease?
1) Adrenal gland failure (1°)
2) ACTH deficiency (2°)
What are 2 symptoms and signs of Addison’s disease?
Adrenal insufficiency → ↓cortisol and aldosterone
1) Fatigue
2) Increased skin pigmentation
3) Hypotension (90/55)
4) HyperK+ (5.6mM) (N: 3.5-5.2)
When is Dexamethasone used at high-dose to discern the source of excess cortisol?
To distinguish between a pituitary and ectopic source
- pituitary will be suppressed @ high dose but ectopic (eg. lung tumour) will not
What is used to assess the source of excess cortisol (Cushing’s syndrome)?
Dexamethasone
If ACTH is low but cortisol is in excess, what is the likely source of excess cortisol?
Adrenal
If ACTH is normal/high but cortisol is in excess, what is the likely source of excess cortisol?
Pituitary or ectopic
- distinguish with high dose dexamethasone
How is the source of cortisol deficiency tested for?
Administer synthetic ACTH
In a primary adrenal gland dysfunction, which hormones would be deficient?
1) Cortisol
2) Aldosterone
How are primary and secondary cortisol deficiencies differentiated?
Administration of synthetic ACTH
- if cortisol restored → 2° issue (can produce, no stimulus/pituitary or hypothalamus issue)
- if cortisol still low → 1° issue (adrenal dysfunction)
What are the differences between primary and secondary adrenal insufficiency?
1) Affected organ
- 1°: adrenal glands affected
- 2°: pituitary/hypothalamus affected
2) Skin
- 1°: dark
- 2°: pale
3) ACTH
- 1°: high
- 2°: not high
4) Aldosterone
- 1°: deficient
- 2°: usually ok
What are 2 conditions of adrenocortical hormone excess?
1) Cushing’s Syndrome:
- DM, 2° HT, Osteoporosis, HypoK+
2) Aldosteronism:
- HT, HypoK+, Metabolic Acidosis
What are 2 conditions of adrenocortical hormone deficiency?
1) Addison’s disease (1°)
2) Congenital adrenal hyperplasia (1°)
3) ACTH deficiency (2°)
What is the name for a tumour in the adrenal medulla and what are the associated symptoms?
Pheochromocytoma
- episodic headache
- sweating
- tachycardia
What is Cushing syndrome?
Hyperadrenocorticism
What are 4 causes of Cushing’s syndrome?
1) Iatrogenic (eg. exogenous glucocorticoids)
2) Cushing’s disease (pituitary ACTH secreting adenoma)
3) Adrenal cortical tumour (adenoma, carcinoma)
4) Ectopic ACTH production (eg. SCC of lung)
