Endocrinology

Question 1

What is the role of ADH?

Answer 1

Produced by the posterior pituitary in response to HYPERTONICITY/ ↑salt in the blood

so if ↑salts then ADH causes fluid reabsorbed to dilute = less urine/more concentrated urine is produced and vice versa

also causes arteriolar vasoconstriction therefore increasing peripheral vascular resistance to increase BP

Question 2

Define diabetes insipidus

What are the two main pathophysiologies?

Answer 2

Excessive urination without glycosuria

1) Nephrogenic - kidneys fail to respond to ADH
2) Cranial - posterior pituitary doesn’t produce enough ADH

Question 3

Give 3 causes of nephrogenic diabetes insipidus

Answer 3

Chronic kidney disease

Iatrogenic e.g. Lithium use

Inherited causes

Question 4

Give 3 causes of cranial diabetes insipidus

Answer 4

Infection e.g. meningitis, encephalitis, TB

Trauma

Hypoperfusion/haemorrhage e.g. Sheehan’s syndrome

Question 5

How does diabetes insipidus normally present?

Answer 5

Polydipsia
Polyuria (>3l per day)
Dehydration

+ hypernatraemia

Question 6

Which blood tests should be ordered to investigate diabetes insipidus and why?

Answer 6

U&E - assess fluid status, check Na+ levels

Urine and serum osmolality - low urine but high serum osmolality

Calcium - hypercalcaemia can cause nephrogenic too

BM - diabetes mellitus presents similarly so need to rule out

Question 7

What bedside/more conservative test can be done to confirm a diagnosis of diabetes insipidus?

Answer 7

Water deprivation test!

Cranial = high urine osmolality after the synthetic ADH as kidneys are still able to respond = water is reabsorbed

Nephrogenic = low osmolality throughout as kidneys don’t respond to ADH

Question 8

What is the difference between primary and secondary adrenal insufficiency?

Answer 8

Primary = Destruction of the zona glomerulosa and zona fasciulata = ↓ mineralocorticoid production (aldosterone) and ↓ glucocorticoid (cortisol)

Secondary = seen upon withdrawal of long term steroids as body becomes reliant on exogenous steroids

Question 9

What are 4 causes of Addison’s/primary adrenal insufficiency?

Answer 9

ADDISONS
TB
Mets
Congenital adrenal hyperplasia

Question 10

What are 4 symptoms of Addison’s?

Answer 10

very non specific
weight loss
N&V
Low mood
unexplained abdo pain

Question 11

What are 3 signs of Addison’s?

Answer 11

Postural hypotension/syncope

Hypogylcaemia

Hyperpigmentation

Question 12

What are the signs of an addisonian crisis?

Answer 12

Signs of shock (↑HR, ↓BP, ↓urine output, altered mental state)

+ known Addisons / known long term steroid user and a precipitating factor e.g. withdrawal, surgery, trauma, infection

Question 13

What is the managment of an addisonian crisis?

Answer 13

Hydrocortisone 100mg IV 6hrly, treat underlying cause, IV fluids


Question 14

What test is diagnostic for Addison’s disease?

Answer 14

Short synacthen test

Question 15

What is the management of Addison’s disease?

Answer 15

Steroid replacement - Hydro or Fludrocortisone = long term

Question 16

Define primary hyperaldosteronism

Answer 16

Excess aldosterone production that is independent of the RAAS

SO ↑ aldosterone/mineralocorticoid

Question 17

What are the two most likely causes of primary hyperaldosteronism and what is the management?

Answer 17

Conn’s Syndrome = adrenocortical adenoma. Mx = surgery

Bilateral adrenal hyperplasia. Mx = spironolactone

Question 18

What are the 3 main features of primary hyperaldosteronism?

Answer 18

Na+ and water retention = Hypertension, fluid overload

Hypokalaemia

Alkalosis

Question 19

What is the function of aldosterone?

Answer 19

Activates and up regulates Na/K pump

Upregulates ENac

Stimulates K+ secretion

↑ Na and water BUT. ↓ K

Question 20

Define secondary hyperaldosteronism

Answer 20

Reduced renal perfusion leads to an increase in Renin production = upregulation of RAAS

Question 21

What are 4 causes of secondary hyperaldosteronism?

Answer 21

renal artery stenosis

CCF

diuretics

liver failure