OSCEs - Endocrine

Question 1

Role of cortisol

Answer 1

Glucocorticoid from the adrenal gland

Increase blood sugar via gluconeogenesis

Fat, protein, and carb metabolism

Anti-inflammatory action

Maintain vascular tone and catecholamine responsiveness

Na retention

Question 2

Where does cortisol come from

Answer 2

Adrenal Cortex - zona fasiculata

CRH - hypothalamus

ACTH - ant pituitary

ACTH to cortex - glucocorticoid secretion - negative feedback

Question 3

Cortisol regulation through the day

Answer 3

Peak in the morning, fall throughout the day, diurnal variation

Levels increased by activity/stress

Pattern reversed in night workers

Question 4

What patterns do you expect in a synacthen test

Answer 4

Pituitary failure -
No ACTH, little cortisol. Low baseline with exaggerated response

Addisons - gland is failing, high ACTH, low cortisol, no response

Question 5

Commonest cause of primary adrenal failure

Answer 5

Auto immune - Addisons

Tumour - myeloid,

TB

Meningococcal sepsis causing Waterhouse Friedrichsen syndrome

Ischaemia

Question 6

What else could you do to establish why a low cortisol

Answer 6

Serum hormones - ACTH, aldosterone, renin

Electrolytes - potassium, sodium

CT adrenals

21-hydroxylase antibody for autoimmune

Question 7

Secondary and tertiary failures

Answer 7

Secondary - no ACTH from pituitary issues -
Tumour, surgery, ischaemia, infarct, Sheehans

Suppression of exogenous glucocorticoid

Tertiary failure of CRH

Question 8

When might we replace cortisol in ITU

Answer 8

Vasopressor refractory shock
Geniuine pit/adrenal failure
When they need long term steroids
BSD

When steroids would be used in medical purposes - anaphylaxis, asthma, COPD, meningococcal disease,

Question 9

Why don’t we do synacthen tests routinely in Itu

Answer 9

Adrenal axis malfunctions therefore cortisol levels vary widely

Cannot identify who really has insufficiency

Question 10

What do you make of normal TSH and T4 with low T3

Answer 10

No raised TSH, so not primary hypothyroid

Sick euthyroid, seen in starvation and critical illness

Question 11

What is sick euthyroid

Answer 11

Abnormal thyroid function tests in the setting of a non-thyroid illness

Without pre-exiting HP axis dysfunction

After recovery, TFTs should reverse (trickier in pre-existing disease)

Most T3 is made outside the thyroid by peripheral conversion from T4. Mechanism fails, so low T3 with normal/high T4. Sometimes T4 low due to low transport protein levels