Prevalence and risk factors for secondary hyperparathyroidism (SHPT) in patients undergoing bariatric surgery

Introduction: Secondary hyperparathyroidism (SHPT) after bariatric surgery has significant adverse implications for bone metabolism, increasing the risk for osteoporosis and fracture. Our aim was to characterize prevalence and identify risk factors for SHPT in bariatric surgery patients.

Methods: We performed a single-institution, retrospective chart review of patients who underwent bariatric surgery from June 2017 through December 2021. Demographic and clinical data were collected, including serum parathyroid hormone, calcium, and vitamin D3 at enrollment and 3, 6, and 12-months postoperatively. Chi-square or Fisher's exact tests were used to analyze categorical data and Mann-Whitney U test for continuous data. Multivariable analysis using binomial logistic regression assessed risk factors for SHPT. P-values ≤ 0.05 were considered significant.

Results: 350 patients were analyzed. SHPT prevalence at any time point was 72.9%. 65.8% had SHPT at enrollment; 45.9% resolved with intensive vitamin supplementation; and 19.7% had recurrent SHPT. New-onset SHPT occurred in 8.6%. Persistent SHPT was present in 42.4% at 1-year. Baseline SHPT correlated with black race and T2DM. SHPT at any time point correlated with T2DM and higher baseline BMI. 1-year SHPT correlated with RYGB, depression, and longer time in program. SHPT was not correlated with %TBWL at any time point. In patients with SHPT, vitamin D3 deficiency prevalence was significantly higher at baseline (77.0%) compared to all post-bariatric time points (16.7%, 17.3%, and 23.1%; P < 0.0001).

Conclusions: SHPT is highly prevalent in patients with obesity seeking weight loss surgery. 42% had persistent SHPT at 1-year despite appropriate vitamin supplementation. Current vitamin D3 and calcium supplementation protocols may not effectively prevent SHPT in many post-bariatric patients. Low prevalence of concomitant vitamin D3 deficiency with SHPT after bariatric surgery suggests that there may be alternative mechanisms in this population. Further studies are needed to develop effective treatment strategies to mitigate the adverse effects of bariatric surgery on bone metabolism.