The impact of post-operative hypoparathyroidism on fractures in a territory-wide cohort of elective total thyroidectomy for benign diseases: a 10-year follow-up

Abstract

Objective: The low bone turnover state in hypoparathyroidism may have potential deleterious effects on bone. Little is known about its impact on fracture risk. As postsurgical hypoparathyroidism is the most common cause of hypoparathyroidism, we assessed its impact on incident fracture risk in a territory-wide cohort of patients who underwent elective total thyroidectomy for benign pathologies. Methods: All elective total thyroidectomies performed in 14 major hospitals across the territory from 1995-2014 were analyzed using an electronic health database. Permanent postsurgical hypoparathyroidism (PPH) was defined by the requirement of oral calcium and calcitriol shortly postoperatively and continued for ≥6 months. Those with albumin-corrected calcium <1.90 mmol/L on ≥1 occasion beyond one year post-operation were considered suboptimally controlled. Fractures were identified by ICD9-CM codes 805 (vertebral), 812 (humeral), 813-814 (wrist and forearm), and 820 (hip). Each patient was followed up until an index fracture, death, or 31 May 2020, whichever was earlier. Multivariable Cox regression analysis was used to identify clinical predictors of fractures. Results: Among 4123 eligible patients, 460 (11.2%) had PPH. Over a median of 10.3 y, 126 patients suffered from an incident fracture (2.77 per 1000 person-years). The median time from thyroidectomy to fracture was 7.2 y. Fracture incidence did not differ between those with and without PPH (2.89 vs. 2.76 per 1000 person-years, respectively, p=0.848). There were no differences in fracture rates over upper extremities, lower extremities and vertebrae between groups. Subgroup analyses according to the adequacy of PPH control did not reveal significant differences in fracture events. Age, history of fall, diabetes and baseline anti-depressant use independently predicted post-thyroidectomy fractures.