MEH 17 - The Adrenal Glands

Question 1

What hormones are released from chromaffin cells of the adrenal medulla?
What are the 3 sections of the the adrenal cortex and what hormones do they release?

Answer 1

Medulla = Adrenaline (80%) + Noradrenaline (20%)
Cortex:
(outside in)
1) Zona glomerulosa - mineralocorticoids e.g.: aldosterone
2) Zona fasciculata - glucocorticoids e.g.: cortisol
3) Zona reticularis - glucocorticoids + angrodens e.g.: DHEA

Good Pneumonic = GFR - Salt, Sugar, Sex :)

Question 2

What type of hormones are all the adrenal hormones?

Therefore, how do they exert their actions?

Answer 2

• Steroid hormone, all synthesised from cholesterol in adrenal glands or gonads
• Bind to nuclear receptors to modulate gene transcription as they are lipid soluble.

Question 3

How do corticosteroids regulate gene transcription?

Answer 3

1) Binding to intracellular receptor causing dissociation of chaperone protein (e.g.: heat shock 90)
2) Receptor/ligand complex migrates to nucleus
3) Receptors bind to glucocorticoid response elements (GRE’s) or other transcription factors

Question 4

What is the central role of aldosterone?

Answer 4

• Promotes expression of Na/K pump. in distal tubules + collecting ducts, influencing water retention and therefore BP (promotes reabsorption of Na+/excretion of K+)
• Drop in BP = activation of RAAS = increased BP

Question 5

What is primary + secondary hyperaldosteronism?
How do you distinguish between the two?
What are the signs + treatment?

Answer 5

1) Primary = defect in adrenal cortex, e.g.: aldosterone secreting adrenal adenoma (Conn’s syndrome).
2) Secondary = overactivity of RAAS, e.g.: renin producing tumour or renal artery stenosis.

• Primary has low renin levels, secondary has high.
• High BP, LV hypertrophy, hypernatraemia, hypokalaemia.
• Remove tumour by surgery, give spironolactone (aldosterone antagonist) for secondary.

Question 6

What are the primary actions of cortisol?

Answer 6

• Increased protein breakdown in muscle
• Increased lipolysis in fat
• Increased gluconeogenesis in liver
• Resistance to stress (increased glucose, raising BP)
• Anti-inflammatory effects

Question 7

What is Cushing’s syndrome?
What are the common causes?
What are the signs + symptoms?

Answer 7

• Chronic excessive exposure to cortisol
• Most commonly caused by prescribed glucocorticoids, much less likely to be a pituitary adenoma secreting ACTH or cortisol producing adrenal tumour
• Moon shaped face, buffalo hump (on neck), abdominal obesity, purple striae, acute weight gain, hyperglycaemia + hypertension.

Question 8

What are steroid drugs often used to treat?

Answer 8

• Inflammatory disorders due to anti-inflammatory effects
• E.g.: asthma, RA, inflammatory bowel disease etc
• E.g.: prednisolone + dexamethasone
• Side effects = higher levels of cortisol

Question 9

What is Addison’s disease?
Who does it affect?
What are the signs + symptoms?

Answer 9

• Chronic adrenal insufficiency, due to destructive atrophy from autoimmune response.
• Affects more women than men
• Postural hypotension, lethargy, weight loss, anorexia, increased skin pigmentation + hypoglycaemia.

Question 10

Why can Addison’s disease cause hyperpigmentation?

Answer 10

• Both ACTH + MSH are synthesised from pro-opiomelanocortin (POMC)
• Less cortisol means less negative feedback on ant pituitary
• More MSH leading to melanin synthesis and hyperpigmentation

Question 11

What is Addison’s crisis + what causes it?

What are the symptoms?

Answer 11

• Life threatening emergency due to adrenal insufficiency - caused by severe stress, salt deprivation, infection, trauma, over exertion etc.
• Nausea, vomiting, pyrexia, hypotension + vascular collapse

Question 12

What is the primary role of male and female androgens?

Answer 12

• In males = DHEA converted to testosterone in testes
• In females = androgens promote libido and converted to oestrogen’s by other tissues
• Promote axillary and pubic hair growth in both sexes

Question 13

What are the affects of AD + NA in the heart, lungs + blood vessels?

Answer 13

• Increased HR + contractility in heart (as B1 receptors, which are GaS)
• Bronchodilation in lungs (as B2 receptors are GaS)
• Vasoconstriction of blood vessels in skin and gut (as a1 are GaQ)
• Vasodilation of skeletal muscle vessels (as B2 receptors are GaS)

Question 14

What is a phaechromocytoma?

What symptoms does it lead to?

Answer 14

• Phae (dark), chromo (colour), cyte (cell) oma (tumour stain dark).
• Basically a chromaffin cell tumour - secreting catecholamines
• Severe hypertension (deadly), headaches, palpitations, diaphoresis + anxiety.