= Excessive and uncontrolled production of parathyroid hormone from neoplastic or hyperplastic parathyroid tissue.
- Usu (+95%) caused by sporadic parathyroid adenoma / sporadic parathyroid hormone hyperplasia.
- Various genetic syndromes assoc with familial 1° hyperparathyroidism, (including MEN-1 and MEN-2) account for only a small proportion of cases.
Excessive PTAH --> osteoclastic resorption --> marked hypercalcemia.
- Patients may be:
- present with signs and symptoms related to hypercalcemia or in a small proportion of cases, present with bone related changes.
In asymptomatic presentations, condition is detected as hypercalcaemia on blood testing for unrelated conditions.
(It should be remembered that there are a number of other causes of hypercalcaemia, including hypercalcaemia associated with malignancy, vitamin D toxicity, immobilisation, some diuretics, and sarcoidosis).
Symptomatic primary hyperparathyroidism reflects both hypercalcaemia and inappropriate and excessive parathyroid hormone secretion.
In addition to osseus disease, described below, there are renal (renal calculi, chronic renal insufficiency), gastro-intestinal (constipation, nausea, peptic ulcers, pancreatitis and gallstones), CNS (depression, lethargy, seizures), neuromuscular (weakness and fatigue) and cardiac (valve calcifications) complications.