Endocrine Surgery (Thyroid, Parathyroid, Adrenal)
The endocrine domain tests the neck and the adrenal gland: thyroid cytology, cancer types, nerve risk, the hypercalcaemia work-up, and perioperative control of a pheochromocytoma. Most marks come from knowing which lesion cannot be diagnosed without histology and which drug must never be given first.
Thyroid
- Nodule work-up: TSH, ultrasound with TIRADS, and FNA reported by Bethesda category I-VI. Bethesda IV (follicular neoplasm) cannot be classified as benign or malignant on cytology - it needs histology.
- Papillary carcinoma: commonest, spreads to lymph nodes, excellent prognosis; total thyroidectomy with or without central neck dissection, then radioiodine.
- Follicular carcinoma: haematogenous spread; diagnostic lobectomy followed by completion thyroidectomy.
- Medullary carcinoma: calcitonin and RET testing, screen for MEN2; total thyroidectomy with central dissection.
- Anaplastic: rapid growth, usually unresectable, palliation only.
- Nerves: recurrent laryngeal nerve injury causes hoarseness and is most likely near the inferior thyroid artery; external branch of the superior laryngeal nerve is injured during ligation of the superior thyroid artery, causing loss of high pitch.
- Postoperative haematoma is an airway emergency - open the wound at the bedside. Hypocalcaemia appears at 24-72 hours; give intravenous calcium if symptomatic.
Parathyroid
- Primary hyperparathyroidism: high calcium, high or inappropriately normal PTH, low phosphate; a single adenoma is the commonest cause.
- Localise with ultrasound and sestamibi; an intraoperative PTH fall of more than 50% confirms cure. Secondary occurs in renal failure; tertiary is autonomous.
Adrenal
- Pheochromocytoma: paroxysmal hypertension, plasma metanephrines, alpha-blockade with phenoxybenzamine for 10-14 days plus volume expansion, then beta-blockade; never beta first.
- Conn adenoma: hypertension with hypokalaemia, raised aldosterone-to-renin ratio. Cushing: cortisol and dexamethasone suppression.
- Incidentaloma: assess size, function and imaging; resect if >4 cm or functional.
Worked example
A 30-year-old with palpitations, sweats and BP 210/110 has raised plasma metanephrines and a 5 cm adrenal mass. Reasoning: pheochromocytoma. Secure alpha-blockade first with volume expansion, add a beta-blocker later for tachycardia, operate only when blood pressure is stable, and anticipate hypertension when the tumour is handled.
Traps
- Giving a beta-blocker first in pheochromocytoma - unopposed alpha effect causes hypertensive crisis.
- Expecting FNA to diagnose a follicular lesion.
- Overlooking ectopic parathyroid glands in the tracheo-oesophageal groove, thymus or mediastinum.
- Discharging a thyroidectomy patient without a plan for hypocalcaemia and haematoma.