The parathyroid glands in multiple endocrine neoplasia type 2b.

The histologic features of 21 parathyroid glands obtained from 16 Mayo Clinic patients aged 2 to 52 years who had multiple endocrine neoplasia type 2b (MEN 2b) were evaluated. The findings were correlated with the patients' ages and with the serum concentrations of calcium (15 patients), phosphorus (14 patients), and immunoreactive parathyroid hormone (iPTH) (11 patients), and with the response of serum iPTH to calcium infusion (6 patients). We also studied the histologic features of 13 parathyroid glands obtained from 8 patients not seen at the Mayo Clinic with MEN 2b. The microscopic appearance of the glands was normal in patients under the age of 17; with increased age, the glands did not exhibit normal involution, and an appearance consistent with mild chief-cell hyperplasia was evident. This abnormality was not associated with clinical or laboratory manifestations of hyperparathyroidism. We presently believe that parathyroidectomy for the disorder is not justified.