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 primary hyperparathyroidism, 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 primary hyperparathyroidism is following by investigations to localize the culprit lesion. Primary hyperparathyroidism 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. Normocalcemic Primary Hyperparathyroidism
Normocalcemic PHPT was first recognized in 2009 by an international panel of experts. By definition these patients have normal serum calcium (though usually in the upper range) and are typically found to have elevated PTH during workup for osteoporosis. In order to diagnose normocalcemic PHPT, ionized calcium levels should be normal, and all secondary causes for secondary hyperparathyroidism (such as vitamin D deficiency and chronic kidney disease) ruled out. Treatment
Treatment is usually surgical removal of the gland(s) containing adenomas, but medication may also be required. Surgery
The surgical removal of one or more of the parathyroid glands is known as a parathyroidectomy; this operation was first performed in 1925.
Symptoms include lethargy, fatigue, depression, memory loss, psychosis, ataxia, delirium, and coma.Left ventricular hypertrophy may also be seen.Other signs include proximal muscle weakness, itching, and band keratopathy of the eyes.When subjected to formal research, symptoms of depression, pain, and gastric dysfunction seem to correlate with mild cases of hypercalcemia. Causes
The most common cause of primary hyperparathyroidism is a sporadic, single parathyroid adenoma resulting from a clonal mutation (~97%). Less common are parathyroid hyperplasia (~2.5%), parathyroid carcinoma (malignant tumor), and adenomas in more than one gland (together ~0.5%).Primary hyperparathyroidism is also a feature of several familial endocrine disorders:  Multiple endocrine neoplasia type 1 and type 2A (MEN type 1 and MEN type 2A), and familial hyperparathyroidism.Genetic associations include:

In all cases, the disease is idiopathic, but is thought to involve inactivation of tumor suppressor genes (Menin gene in MEN1), or involve gain of function mutations (RET proto-oncogene MEN 2a).Recently, it was demonstrated that liquidators of the Chernobyl power plant are faced with a substantial risk of primary hyperparathyroidism, possibly caused by radioactive strontium isotopes. Diagnosis
The diagnosis of primary hyperparathyroidism is made by blood tests.Serum calcium levels are usually 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 primary hyperparathyroidism.A more powerful variant of comparing the balance between calcium and parathyroid hormone is to perform a 3-hour calcium infusion.