There are 3 types of familial hyperparathyroidism:
1. MEN-1 (the parathyroid disease is severe; please see section on MEN-1 for discussion)
2. MEN-2 (the parathyroid disease is mild; please see section on MEN-2 for discussion)
3. Familial hypocalciuric hypercalcaemia (also known as familial benign hypercalcaemia). This fascinating disease is not a surgical entity, except in neonates with severe hypercalcaemia. The cause is a genetic defect in the parathyroids' "calcium sensor". Because the sensor is incorrectly set the serum calcium is maintained at abnormally high levels. The family history, mild hypercalcaemia, detectable parathyroid hormone level and low urinary calcium excretion make the diagnosis. It is a condition that is a trap even for the most experienced endocrine surgeon.