Clinical aspects of hyperparathyroidism in Japanese multiple endocrine neoplasia type 1.

We describe here the clinical aspects of hyperparathyroidism (HP) in Japanese multiple endocrine neoplasia type 1 (MEN 1). The total number of MEN 1 patients was 37, and they originated from ten unrelated Japanese families. Nine of the ten families were proven to have heterozygous germline mutations of the MEN 1 gene. The incidence of HP, pituitary tumors, and pancreatic tumors in 37 MEN 1 patients was 91.9%, 32.4%, and 45.9%, respectively. The age-related penetrances of HP were 50%, 79%, 84%, by 20, 30, and 40 years of age, respectively. Of these MEN 1 patients, we used 28 individuals, diagnosed with HP at our hospitals, to study the clinical aspects of MEN 1-associated HP. The mean age was 40 years, and the mean was much lower in the sporadic (non-MEN 1) HP patients. The mean levels of calcium, phosphate, and intact PTH were 10.8 mg/dL, 2.3 mg/dL, and 178.0 pg/mL, respectively, and these were not different from those of sporadic HP patients. The levels of intact PTH were positively correlated with age, suggesting that HP may be progressive with time in MEN 1. The percentage of symptomatic HP was 36% in MEN 1, whereas it was 55% in sporadic HP patients. Although histopathological findings revealed that all four parathyroid glands were involved in hyperplasia, imaging studies showed an enlargement of only the single parathyroid gland in most patients. The combination of total parathyroidectomy and autoplantation succeeding in improving HP in MEN 1.