Primary hyperparathyroidism is confirmed by demonstration of an inappropriately high PTH level for the degree of hypercalcemia. Hypercalciuria helps to distinguish this disorder from FHH, in which PTH levels are usually in the normal range and the urine calcium level is low. Differentiation between primary hyperparathyroidism and FHH is important because the latter does not respond to parathyroid surgery. Levels of PTH are low in hypercalcemia of malignancy (Table 176-2).
Total serum calcium should be corrected when serum albumin is abnormal (addition of 0.2 mM [0.8 mg/dL] to calcium value for every 1.0-g/dL decrement in albumin below 4.1 g/dL, or the converse for an increase in albumin). Alternatively, ionized calcium can be measured. Third-generation PTH assays should be used for PTH measurement, especially in pts with renal impairment.
Treatment: Hypercalcemia The type of treatment is based on the severity of the hypercalcemia and the nature of the associated symptoms. Table 176-3 shows general recommendations that apply to therapy of severe hypercalcemia (levels of >3.2 mmol/L [>13 mg/dL]) from any cause. In pts with severe primary hyperparathyroidism, surgical parathyroidectomy should be performed promptly. Asymptomatic disease may not require surgery; usual surgical indications include age <50, nephrolithiasis, creatinine clearance <60 mL/min, reduction in bone mass (T score <-2.5), or serum calcium >0.25 mmol/L (>1 mg/dL) above the normal range. A minimally invasive approach may be used if preoperative localization via sestamibi scans with single-photon emission computed tomography (SPECT) or neck ultrasound demonstrates a solitary adenoma and intraoperative PTH assays are available. Otherwise, neck exploration is required. Surgery in a center experienced in parathyroid interventions is recommended. Postoperative management requires close monitoring of calcium and phosphorus, as transient hypocalcemia is common. Calcium supplementation is given for symptomatic hypocalcemia. Hypercalcemia of malignancy is managed by treating the underlying tumor. Adequate hydration and parenteral bisphosphonates can be used to reduce calcium levels. Long-term control of hypercalcemia is difficult unless the underlying cause can be eliminated. No therapy is recommended for FHH. Secondary hyperparathyroidism should be treated with phosphate restriction, the use of nonabsorbable antacids or sevelamer, and calcitriol. Tertiary hyperparathyroidism requires parathyroidectomy. |
Section 13. Endocrinology and Metabolism