Hyperparathyroidism
Definition
Hyperparathyroidism is a condition characterized by hypercalcaemia caused by excess production of parathyroid hormone (PTH).
Key Points
- Hyperparathyroidism often presents with vague symptoms to many different specialists.
- Asymptomatic hypercalcemia is most common clinical presentation of primary hyperparathyroidism.
- Surgery is the treatment of choice for primary hyperparathyroidism.
- Hypoparathyroidism post surgery is rare and mostly transient.
Causes
- Primary hyperparathyroidism (PHPT) is usually due to a parathyroid benign adenoma (75%) or parathyroid hyperplasia (20%). 1.0% have parathyroid carcinoma.
- Secondary hyperparathyroidism is hyperplasia of the gland in response to hypocalcaemia (e.g. in chronic renal failure).
- In tertiary hyperparathyroidism, autonomous secretion of parathormone occurs when the secondary stimulus has been removed (e.g. after renal transplantation).
- MEN syndromes (type I (parathyroid adenoma, pancreatic islet cell tumours, pituitary adenoma) and type II (parathyroid adenoma, medullary thyroid cancer, phaeochromocytoma) and ectopic parathormone production (e.g. from small cell lung cancer).
Pathology
Parathormone mobilizes calcium from bone, enhances renal tubular absorption and, with vitamin D, intestinal absorption of calcium. The net result is hypercalcaemia.
Clinical Features
- Older women, >40 years of age.
- Renal calculi or renal calcification – occurs in 20% of patients, polyuria (‘renal stones’).
- Bone pain or deformity, osteitis fibrosa cystica, pathological fractures (‘painful bones’).
- Muscle weakness, anorexia, intestinal atony, psychosis (‘psychic moans’).
- Peptic ulceration and pancreatitis (‘abdominal groans’).
Diagnosis
Laboratory
- Elevated PTH in the setting of hypercalcaemia.
- Serum calcium (specimen taken on three occasions with patient fasting, at rest and without a tourniquet). Normal range 2.2–2.6 mmol/L. Calcium is bound to albumin and the level has to be ‘corrected’ when albumin levels are abnormal.
- May be decreased serum phosphate and elevated alkaline phosphatase.
Imaging
- High-resolution ultrasound.
- 99mTc sestamibi scintigraphy ± sestamibi-single photon emission computed tomography (SPECT).
- CT and MRI scanning.
- DXA scans for bone density measurement in all patients with hyperparathyroidism.
- Selective vein catheterization and digital subtraction angiography in patients in whom exploration has been unsuccessful.
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