Bone Abstracts

Background: Hypoparathyroidism (HypoPT) is a rare disease, characterized by low plasma levels of Parathyroid hormone and calcium. Furthermore it is characterized by high BMD and very low bone turnover.

Aim: We studied risk of fracture in patients with postsurgical HypoPT due to non-malignant diseases compared with an age- and gender-matched control group.

Method: We performed a controlled cohort study. Patients diagnosed with HypoPT due to neck surgery for non-malignant causes from 1988 to 2012 were identified using the National Patient Registry on hospital discharge diagnoses. In addition, patients were identified through regional prescription databases, by identifying patients on treatment with active vitamin D analogues. Case status of all identified patients was subsequently validated by review of their medical charts. For each patient, we received three age- (±2 years) and gender-matched controls, randomly selected from the general background population. Risk of fracture was calculated by Cox regression analyses.

Results: Within a population of 5,336,394 persons, we identified 688 patients with chronic HypoPT due to non-malignant disease (prevalence 22/100,000). Risk of any fracture did not differ between cases and controls (crude HR 0.97, 95% CI 0.77–1.21). Adjustment for a history of fracture did not change results (HR 0.95, 95% CI 0.76–1.18). Analysing risk at specific skeletal sites showed a decreased fracture risk at the upper extremities (HR 0.69, 95% CI 0.49–0.97, P=0.048), whereas risk of a vertebral fracture (HR 1.05, 95% CI 0.0.55–1.97) or risk of fracture at the lower extremities (HR 1.07, 95% CI 0.77–1.49) did not differ between groups. Neither did risk of an atypical (Subtrochanteric) femoral fracture differ between groups (HR 1.29, 95% CI 0.37–4.20).

In conclusion, patients with postsurgical HypoPT for non-malignant diseases do not have an increased risk of fractures; rather risk of fractures at the upper extremities is reduced compared with healthy age- and gender-matched controls.