Adrenal Function

Question 1

1. What hormones does the adrenal cortex produce and from which layers?

Answer 1

Adrenal cortex has 3 layers and produce different hormones each

Zona Glomerulosa -> mineralocorticoids (aldosterone)

Zona Fasiculata -> glucocorticoids (cortisol)

Zona Reticularis -> androgens/oestrogen (DHEA (dehydroepiandosterone) and oestradiol)

Question 2

2. Describe the effects of aldosterone?

Answer 2

Released in response to RAAS system to maintain BP -Acts by means of salt and therefore fluid retention

Reabsorption of Sodium in the DCT and collecting ducts of the kidney, sweat glands, salivary glands and gut

Excretion of potassium – active exchange with sodium ions

H+ loss – may also be exchanged with Na ions, which may lead to a metabolic alkalosis

Water – increasing serum Na+ = stimulation of pituitary osmoreceptors with lead to increased release of ADH = water retention and returns Na to normal at the expense of increased circulating volume

Question 3

What causes on increase in aldosterone release?

Answer 3

Hypovolaemia/reduced renal perfusion and reduced presentation of sodium to the kidneys macula densa -> stimulates RAAS. Increased renin secretion -> increase in serum angiotensin II = increase aldosterone.

Decreased plasma Na+

Increased plasma K-

Question 4

4. What reduces aldosterone secretion?

Answer 4

Hypernatraemia

Hypervolaemia / reduced renin secretion

Hypokaleamia

INcreased circulating ANP – this has an inhibitory effect on renin

Question 5

What is Cushing’s Disease / Syndrome ?

Answer 5

Cushing’s disease/syndroms is where there is an excess of glucocorticoid production from an endogenous or exogenous source.

Question 6

What are the causes of cushings syndrome / disease?

Answer 6

Exogenous:

Steroids – iatrogenic

Pseudo-cushings: ETOH excess, depression

Endogenous:

ACTH Dependent:

Pituitary secreting ACTH

Ectopic ACTH secretion: SCLCa, cacinoid. Presents with hyperpigmentation, hypokalaemic alkalosis, weight loss

ACTH Independent (ACTH due to negative feedback):

Adrenal adenoma or carcinoma

Question 7

What are the signs and symptoms of Cushing’s Disease/Syndrome?

Answer 7

Bi-temporal hemianopia – if pituitary tumour

Central obesity / weight gain

Coarse/Thin skin

Poor wound healing

Easy bruising

Proximal myopathy

Striae

Fluid retention/Oedema

Virilisation-excess hair

Deep voice

Tiredness

Depression

Headaches

Question 8

What are the causes of excess aldosterone production?

Answer 8

Primary Hyperaldosteronism:

Conn’s Syndrome (adrenal adenoma) 60-70%

Bilateral hyperplasia – 20-30%

Secondary hyperaldosteronism: (excess secretion of renin)

RAS

Heart failure

Liver cirrhosis

Question 9

What are the signs and symptoms of conn’s syndrome?

Answer 9

Hypokalaemia – associated muscle weakness

Hypernatraemia and Fluid retention – associated hypertension. Can by hyperNa or normo – depending on ratio of water conserved

H+ loss – associated metabolic alkalosis

Question 10

What would the urine of a Conn’s syndrome patient show?

Answer 10

Low sodium

High potassium

High aldosterone concentrations

Question 11

What are the causes of Addisons Disease?

Answer 11

Hypoaldrenalism

Primary – destruction of the adrenal cortex

Autoimmune (>80%)

Infection: TB (20%)

Haemorrhage – waterhouse-friedreichsen syndrome (meningococcal septiceamia), antiphospholipid syndrome, anticoagulants

Malignant infiltration: sarcoid, amyloid, tumour

Iatrogenic: adrenalectomy, ketoconazole, metyrapone

Secondary – pituitary disease and resulting decrease in ACTH secretion, only affecting glucocorticoids

Question 12

What are the signs and symptoms of Addisons disease?

Answer 12

Signs: Hyperpigmentation, postural hypotension, muscle wasting and vitiligo

Symptoms: dizziness, fatigue, weightloss nausea, poor appetite

Question 13

What baseline bloods would show in addisons?

Answer 13

Mineralocorticoid deficiency:

Hyperkalaemia

Hyponatraemia

Metabolic acidosis

Glucocorticoid deficiency: hypoglycaemia

Question 14

How does the embryonic origin of the adrenal cortex differ from that of the medulla?

Answer 14

Adrenal cortex is from mesoderm

Adrenal medulla is from neuro-ectoderm

Question 15

What is the innervation of the adrenal medulla?

Answer 15

Sympathetic nervous system

Contains chromaffin cells whish are specialised post-ganglionic sympathetic neurons

Nerve fibers from splanchnic nerves innervate the medulla, releasing acetylcholine, which stimulates hormone release.

Acetylcholine = neurotransmitter

Question 16

Describe phaechromocytoma

Answer 16

Phae is a catecholamine secreting tumour, normally found in the medullar of the adrenal gland

Rule of 10s:

10% are extra-adrenal, bilateral, familial (MEN, VHL), malignant