Characteristics of Primary Hyperparathyroidism in Multiple Endocrine Neoplasia Type 2A

Objective: Multiple endocrine neoplasia type 2A (MEN2A) is an autosomal dominantly inherited tumour syndrome and primary hyperparathyroidism (pHPT) is one of the major components of MEN2A. Our study evaluated the features of MEN2A-related hyperparathyroidismMaterial and Methods: Records of 49 patients with MEN2A followed up at Istanbul Faculty of Medicine were retrospectively reviewed.Results: This study included 25 females and 24 males, and 55% of the patients had RET 634 variants. The median follow-up duration was 12 years. Medullary thyroid cancer (MTC) was present in 44 patients, and the mean age at diagnosis was 30.8±14 years. Pheochromocytoma was detected in 61% of patients, and the mean age at diagnosis was 36.4±12.6 years. Twelve patients (F/M=1) had pHPT, and the mean age at diagnosis was 40±15.7 years. The frequency of pHPT was 6% in the ATA moderate-risk category and 33.3% in the high-risk category (RET 634 variants). pHPT developed in 3 of 4 patients carrying the RET C634R variant. The most common symptoms were nephrolithiasis and osteoporosis, and 67% of patients had normocalcemic pHPT. Selective surgery was performed in 9 patients and subtotal parathyroidectomy in 1 patient. The median follow-up duration after the diagnosis of pHPT was 10.5 years, and persistent disease developed in 1 patient. Recurrent hyperparathyroidism occurred in 1 patient 12 years after the first operation. Five patients developed permanent hypoparathyroidism.Conclusion: The RET mutation at codon 634 is associated with a high frequency of pHPT, usually accompanied by normocalcemia or, less frequently, mild hypercalcemia.