endocrine and metabolic disorders
Hyperparathyroidism
Diagnosis of Hyperparathyroidism
Serum calcium, phosphate, and PTH measurement The diagnosis of primary hyperparathyroidism should be made based on blood and urine tests and clinical findings. A diagnosis of hyperparathyroidism is usually first suspected when elevated serum calcium is found on routine blood tests. If calcium remains high on repeat testing, intact PTH should be checked and interpreted with the calcium level. Patients with primary hyperparathyroidism have a high PTH concentration in the absence of hypocalcemia. A minority of patients have a high-normal PTH concentration, which should be interpreted as inappropriate when the calcium concentration is elevated (and suppression of PTH would normally be expected— Diagnosis reference ). In hyperparathyroidism, the serum calcium is rarely > 12 mg/dL (> 3 mmol/L), but the ionized serum calcium is almost always elevated. Low serum phosphate concentration suggests hyperparathyroidism, especially when coupled with elevated renal excretion of phosphate. When hyperparathyroidism results in increased bone turnover, serum alkaline phosphatase is frequently increased. Urinary calcium excretion is usually normal or high in hyperparathyroidism. Low urinary calcium suggests another diagnosis such as Familial hypocalciuric hypercalcemia . Chronic kidney disease suggests the presence of secondary hyperparathyroidism, but primary hyperparathyroidism can also be present. In patients with chronic kidney disease, high serum calcium and normal serum phosphate suggest primary hyperparathyroidism, whereas elevated phosphate suggests secondary hyperparathyroidism. Imaging studies of the parathyroid(s) may be done preoperatively to localize an abnormal gland; it is not done to establish the diagnosis or determine whether surgery is needed. However, parathyroidectomy done by experienced surgeons has a high cure rate, and this has not been improved with use of preoperative imaging. Many imaging techniques have been used effectively, including the following: High-resolution CT with or without CT-guided biopsy and PTH immunoassay from thyroid venous drainage Contrast-enhanced four-dimensional (4D) CT MRI High-resolution ultrasonography Digital subtraction angiography Thallium-201–technetium-99 scanning Technetium-99 sestamibi, a radionuclide agent for parathyroid imaging, is more sensitive and specific than older agents and may be useful for identifying solitary adenomas. For residual or recurrent hyperparathyroidism after initial parathyroid surgery, imaging is necessary and may reveal abnormally functioning parathyroid glands in unusual locations throughout the neck and mediastinum. Technetium-99 sestamibi is probably the most sensitive imaging test for these glands. Use of several imaging studies (MRI, CT, or high-resolution ultrasonography in addition to technetium-99 sestamibi) before repeat parathyroidectomy is sometimes necessary. 1.Bilezikian JP, Khan AA, Silverberg SJ, et al: Evaluation and management of primary hyperparathyroidism: Summary statement and guidelines from the Fifth International Workshop.J Bone Miner ResAug. 19, 2022. doi: 10.1002/jbmr.4677 