The diagnosis of<unk>  is made by blood tests. Serum calcium levels are elevated, and the parathyroid hormone level is abnormally high compared with an expected low level in response to the high calcium. A relatively elevated parathyroid hormone has been estimated to have a sensitivity of 60–80% and a specificity of approximately 90% for<unk> . A more powerful variant of comparing the balance between calcium and parathyroid hormone is to perform a 3-hour calcium infusion. After infusion, a parathyroid hormone level above a cutoff of 14 ng/l has a sensitivity of 100% and a specificity of 93% in detecting<unk> , with a confidence interval of 80% to 100%. Urinary cAMP is occasionally measured; it is generally elevated due to activation of Gs proteins when PTH binds to its receptor. Biochemical confirmation of<unk>  is following by investigations to localize the culprit lesion.<unk>  is most commonly due to solitary parathyroid adenoma. Less commonly it may be due to double parathyroid adenomas or parathyroid hyperplasia. Tc99 sestamibi scan of head, neck and upper thorax is the most commonly used test for localizing parathyroid adenomas having a sensitivity and specificity of 70–80%. Sensitivity falls down to 30% in case of double/multiple parathyroid adenomas or in case of parathyroid hyperplasia. Ultrasonography is also a useful test in localizing suspicious parathyroid lesions.
Primary hyperparathyroidism
Secondary hyperparathyroidism
Tertiary hyperparathyroidism
Familial hypocalciuric hypercalcemia
Parathyroid adenoma
Pseudohypoparathyroidism
Normophosphatemic familial tumoral calcinosis
Pseudopseudohypoparathyroidism