Increased risk of vertebral fractures and reduced risk of femur fractures in patients with chronic hypoparathyroidism: a nationwide cohort study in Sweden.

Patients with chronic hypoparathyroidism (hypoPT) have reduced bone remodeling, leading to increased bone density and abnormalities in microarchitecture and bone strength. Whether these patients have an increased fracture risk remains unclear. This study aimed to evaluate the risk of major osteoporotic fracture (MOF), osteoporosis diagnoses, and osteoporosis medication use in patients with chronic hypoPT in Sweden. Subtypes of fractures were also assessed. Using the Swedish National Patient Register, the Prescribed Drug Register, and the Total Population Register, we identified 1915 patients with chronic hypoPT treated with active vitamin D between 1997 and 2018, and 15 838 matched controls. After adjustment, patients with chronic hypoPT did not have a higher risk of MOF compared to controls (HR 0.93; 95% CI: 0.69-1.26). However, they had a higher risk of vertebral fractures (HR 1.55; 95% CI: 1.12-2.14) and a lower risk of femur fractures (HR 0.70; 95% CI: 0.50-0.98) compared to controls. They were more often diagnosed with osteoporosis (HR 1.54; 95% CI: 1.21-1.95) but less frequently prescribed osteoporosis medication (HR 0.69; 95% CI: 0.54-0.88) compared to controls. No difference in the MOF risk was observed between females and males (p for interaction = 0.872) or between patients with surgical and non-surgical chronic hypoPT (p for interaction = 0.072). In this large Swedish cohort, chronic hypoPT was not associated with an increased risk of MOF. Vertebral fracture risk was higher, while the femur fracture risk was lower compared to controls. Despite higher prevalence of osteoporosis diagnoses, these patients received less frequently osteoporosis medications.