Multiglandular parathyroid disease
A single adenoma is, by far, the most common cause of primary HPT (85%). Depending on the method used to define multiglandular disease (i.e., ioPTH assay versus gross appearance/size), the reported rates range from 5% to 35%. Multiglandular disease can be caused by either multiple adenomas or four-gland hyperplasia. Hyperplasia may be sporadic or secondary to a genetic predisposition, such as MEN syndrome. When all four glands are hyperplastic, a subtotal parathyroidectomy is required (removal of 3½ glands). It is important that the surgeon be careful to preserve the blood supply to the parathyroid remnant. If after removing half the final parathyroid the remnant appears ischemic, then it should be excised and autotransplanted, either to the brachioradialis muscle in the nondominant forearm or the sternocleidomastoid muscle. Most patients (95%) will have normal calcium and low or normal parathyroid hormone levels; however, permanent hypoparathyroidism occurs in 2% to 3% and recurrent hyperparathyroidism occurs in about 10% of patients.