Endocrinology and Metabolism
This domain tests diabetes diagnosis and drug selection, diabetic emergencies, thyroid disease and adrenal insufficiency - conditions where sequencing of treatment determines outcome.
Diabetes
Diagnose with HbA1c of 6.5% or more, fasting glucose of 126 mg/dL or more, a 2-hour value of 200 mg/dL or more, or random glucose of 200 mg/dL or more with symptoms. Metformin remains first line; add an SGLT2 inhibitor or GLP-1 receptor agonist early when atherosclerotic disease, heart failure or chronic kidney disease coexists.
DKA and HHS
DKA shows glucose above 250 mg/dL, pH below 7.3, bicarbonate below 18 mmol/L and ketonaemia. HHS shows glucose above 600 mg/dL, osmolality above 320 mOsm/kg and minimal ketosis. Give isotonic fluid first, then insulin at 0.1 units/kg/h only once potassium is 3.3 mmol/L or above; add dextrose when glucose falls to 200–250 mg/dL and continue insulin until the anion gap closes.
Thyroid disease
Primary hypothyroidism shows a high TSH with low free T4; subclinical disease shows a high TSH with normal free T4. Thyroid storm is a clinical diagnosis: give a beta-blocker, thionamide, iodine at least an hour after the thionamide, and glucocorticoid.
Adrenal crisis
Give hydrocortisone 100 mg intravenously immediately; do not wait for a cortisol result.
Worked example
A patient in DKA arrives with potassium 3.0 mmol/L. Hold insulin, give intravenous potassium, and only start the infusion once potassium is above 3.3 - insulin would drive potassium intracellularly and risk arrhythmia.
Traps that cost marks
- Starting insulin before fluids and before confirming potassium.
- Giving bicarbonate unless pH is below 6.9.
- Stopping the insulin infusion as soon as glucose normalises, before gap closure.