Phenotypic Features and Bone Metabolism in MEN1-related Hyperparathyroidism According to the Russian Registry of Hyperparathyroidism

BACKGROUND: MEN1-related hyperparathyroidism (mPHPT) is a rare inherited form of primary hyperparathyroidism (PHPT) that is caused by a germline mutation in the MEN1 gene. The available data on bone phenotypes in mPHPT are scarce and contradictory due to the orphan nature of the disease, the under-recognition of the disease due to the limited use of genetic screening, and the heterogeneity of the samples evaluated. AIM: To evaluate the phenotypic features of verified MEN1-associated primary hyperparathyroidism, including associated bone complications, according to data from Russian register of primary hyperparathyroidism MATERIALS AND METHODS: A nationwide, multicenter, non-interventional, observational, cross-sectional study was conducted to investigate the characteristics of bone metabolism in a group of verified mPHPT (N=86) and sporadic hyperparathyroidism (sPHPT) (N=3599) in the active phase of PHPT. The main parameters of calcium-phosphorus metabolism were evaluated, as well as bone mineral density (BMD) using the Z-score in the lumbar spine, femur, and radius. RESULTS: According to the Russian registry of hyperparathyroidism, patients with mPHPT have the same parameters of calcium-phosphorus metabolism as the sporadic form of the disease, with higher levels of total (p=0.019) and the lower level of ionized calcium (p=0.010). The prevalence of isolated bone complications (38% vs. 27%; p=0.081) and renal pathology (16% vs. 18%; p=0.086) was comparable in both groups. After exclusion of age-related factors, the bone phenotype of mPHPT is characterized by a greater frequency of BMD loss in the femur neck (p=0.009). CONCLUSION: According to data from the Russian Registry of Hyperparathyroidism, patients with mPHPT and sPHPT are characterized by comparable deviations in the main parameters of phosphorus-calcium metabolism, except for total and ionized calcium, as well as the frequency of bone and visceral complications. A higher frequency of BMD loss at the femoral neck was observed in the subgroup of young patients with mPHPT.