Primary hyperparathyroidism - caused by a single adenoma (>80%) or diffuse hyperplasia of the parathyroid glands (15-20%)
Tertiary hyperparathyroidism
Malignant disease
Metastatic bone destruction
PTHrp from solid tumours
Osteoclast activating factors produced by tumours
Genetic syndromes
MEN1 and 2 - will almost always have developed a parathyroid adenoma with hypercalcaemia at a young age
Familial isolated hyperparathyroidism - adenoma as in primary hyperparathyroidism
Familial hypocalciuric hypercalcaemia - autosomal dominant deactivating mutation in the calcium sensing receptor which results in decreased sensitivity of the receptor to calcium