Primary hyperparathyroidism

Effect · Ca up, PO4 down PTH up

Autonomous PTH secretion, most often from a single adenoma. Hypercalcaemia with a PTH that is raised or inappropriately within the reference range, a low phosphate and hypercalciuria. Most cases are now picked up incidentally on a biochemistry panel.

Traced from the start

Detail

Biochemistry: Calcium high, phosphate low, PTH high or inappropriately normal, urinary calcium high, alkaline phosphatase normal or raised, calcitriol high or high-normal, and a mild hyperchloraemic acidosis
Causes: Solitary adenoma about 85%, four-gland hyperplasia 10-15% (MEN 1, MEN 2A), carcinoma under 1%, which presents with a very high calcium and a palpable neck mass
Must exclude: Familial hypocalciuric hypercalcaemia, using the urinary calcium:creatinine clearance ratio (below 0.01 suggests FHH); also stop lithium and thiazides before interpreting
Localisation: Sestamibi scan with ultrasound, or 4D CT, done only after the diagnosis is biochemical; intraoperative PTH confirms cure
Surgery indicated by: Calcium more than 0.25 mmol/L above the upper reference limit, age under 50, eGFR below 60 mL/min, T-score of -2.5 or lower or a vertebral fracture, 24-hour urinary calcium above 10 mmol, or nephrolithiasis

When it goes wrong

Asymptomatic hypercalcaemia found on a routine panel

The commonest presentation; confirm with a simultaneous calcium and PTH and exclude familial hypocalciuric hypercalcaemia before offering parathyroidectomy

Symptomatic primary hyperparathyroidism

Renal stones, osteoporosis and fragility fracture, constipation, peptic ulcer, pancreatitis, depression and cognitive slowing: stones, bones, abdominal moans and psychic groans

Practise this structure

1 question in the bank tagged Parathyroid.

A 58-year-old man is found to have a serum calcium concentration of 2.78 mmol/L (2.15–2.55) on two occasions. His phosphate is 0.72 mmol/L (0.80–1.50), creatini…

Clinical rotations · common