Describe Primary Hyperparathyroidism in detail.

The Concept

Primary hyperparathyroidism is the autonomous over-secretion of parathyroid hormone (PTH) by the parathyroid glands themselves, independent of the normal calcium feedback. Because PTH raises serum calcium (by releasing it from bone, increasing renal reabsorption and activating vitamin D), the result is hypercalcaemia with an inappropriately high PTH — the biochemical signature of the disease. The commonest cause (~85%) is a single parathyroid adenoma; less often it is four-gland hyperplasia or, rarely, a carcinoma.

Clinical Features — the Effects of Hypercalcaemia

Many patients are asymptomatic (found on a routine calcium), but symptomatic disease is remembered by the classic mnemonic 'bones, stones, groans and psychic moans': bone pain and osteoporosis (and the specific lesion osteitis fibrosa cystica), renal stones and polyuria, abdominal groans (constipation, peptic ulcers, pancreatitis), and psychiatric moans (depression, lethargy, confusion). Severe hypercalcaemia causes dehydration and cardiac arrhythmia (short QT).

Diagnosis & Management

The diagnosis is biochemical: a raised serum calcium together with a raised or inappropriately normal PTH (with a low phosphate). The adenoma is then localised with a sestamibi scan and ultrasound. Definitive treatment of symptomatic or significant disease is surgical — parathyroidectomy (removing the single adenoma, or all four glands with autotransplantation in hyperplasia). Acute severe hypercalcaemia is managed medically first with IV fluids (rehydration) and bisphosphonates.

Secondary & Tertiary Hyperparathyroidism

• It helps to contrast the types.
• Primary is autonomous PTH excess with high calcium.
• Secondary hyperparathyroidism is an appropriate compensatory rise in PTH in response to a low calcium (classically chronic kidney disease with vitamin D deficiency) — here PTH is high but calcium is low or normal.
• Tertiary occurs when longstanding secondary stimulation makes the glands autonomous, so they oversecrete even after the cause is corrected (e.g. After renal transplant), producing high calcium again.

Biochemistry & Surgical Planning

The biochemical hallmark — a raised calcium with an inappropriately high or normal PTH — distinguishes primary hyperparathyroidism from the far commoner malignant hypercalcaemia (in which PTH is suppressed). Once confirmed, the adenoma is localised (sestamibi scan and ultrasound, sometimes 4D-CT), enabling minimally invasive, focused parathyroidectomy rather than four-gland exploration where a single adenoma is clearly seen. Intra-operative PTH measurement (which falls sharply once the adenoma is removed) confirms cure on the table — an elegant use of the hormone's short half-life.

The Bottom Line

In summary, primary hyperparathyroidism is diagnosed biochemically (high calcium with inappropriate PTH), localised by sestamibi and ultrasound, and cured by parathyroidectomy, with acute severe hypercalcaemia managed first by rehydration and bisphosphonates — a clean, logical sequence from biochemistry to cure.

Raised calcium with an inappropriately normal or high PTH is diagnostic.

• Primary hyperparathyroidism = autonomous PTH excess → hypercalcaemia with inappropriately high PTH.
• Cause: solitary adenoma (~85%), hyperplasia, rarely carcinoma.
• Features: 'bones, stones, groans, psychic moans' — bone pain/osteoporosis, renal stones, abdominal symptoms, psychiatric changes.
• Diagnose: high calcium + high/inappropriate PTH + low phosphate; localise with sestamibi + ultrasound.
• Treat by parathyroidectomy; acute severe hypercalcaemia → IV fluids + bisphosphonates.