This disorder occurs with a prevalence of approximately 1 in 1000 with a female to male ratio of approximately 3:1. Hyperparathyroidism is a disorder of the elderly with the majority of patients being older than 50 years of age. A single hyperfunctioning parathyroid adenoma is the underlying pathology in 85% of cases, and hyperplasia of multiple parathyroid glands accounts for the majority of the remaining 15%. Rarely, this disorder may result from parathyroid carcinoma (0. 5-4.0%). This disorder is relatively asymptomatic until severe hypercalcemia causes symptoms, and the diagnosis is usually made when hypercalcemia and hypophosphatemia or mild hyperchloremic acidosis are noted on routine labs. These abnormalities should prompt the physician to order a parathyroid hormone (PTH) assay. The diagnosis is firmly secure when the PTH is elevated in the presence of hypercalcemia; however, this may occur in three other conditions (lithium intake, familial hypocalciuric hypercalcemia, or ectopic PTH secretion by tumors) that occur with much less frequency. Primary hyperparathyroidism may also be diagnosed when hypercalcemia is present and the serum PTH is normal (the PTH should be suppressed in the presence of hypercalcemia so a normal PTH indicates impaired suppression of the parathyroid gland). Hyperparathyroidism is a common component of multiple endocrine neoplasia syndrome type 1 and patients with concomitant hypertension should be evaluated for an underlying pheochromocytoma as they may suffer from underlying multiple endocrine neoplasia syndrome type 2A.
Side effects of this disorder include nephrolithiasis and osteitis fibrosa cystica. The latter is a bone disease in which demineralization occurs followed by increased osteoclastic activity with bone resorption and fibrosis. The bony changes are correctable with proper treatment of the hyperparathyroidism.
Treatment of this condition entails either close monitoring if the elevation of calcium is minimal and without symptoms or surgical removal of the pathologic parathyroid gland or glands. Radiographic isolation of the pathology prior to surgery with Technitium99m sestamibi scanning is not indicated because no test is as sensitive as visual isolation of the pathology by a qualified surgeon. Mild asymptomatic hypercalcemia secondary to primary hyperparathyroidism may, under the proper circumstances, require only close observation rather than surgery. Indications for surgery include the following: significant hypercalcemia greater than 1.0 mg/dL above normal, prior life-threatening hypercalcemia, kidney stones detected on abdominal radiography, significantly elevated 24-hour urine calcium value (greater than 400 mg/day), or a decreased bone mass (decreased more than 2.5 standard deviations for age-matched, gender-matched, and race-matched controls). Patients deemed to be potentially noncompliant with follow-up care should also be considered for surgery. Surveillance entails measuring the serum calcium every six months, annual creatinine measurements, and DEXA scanning of the spine, hip, and forearm annually.