Obesity Abstracts

Introduction: Obesity is a major global health concern, and bariatric surgery is an established treatment for sustained weight loss and metabolic improvement. Gastric bypass bypasses the duodenum and proximal jejunum—the primary sites of calcium absorption—altering calcium–parathyroid hormone (PTH) metabolism and predisposing to secondary hyperparathyroidism (SHPT). The British Obesity and Metabolic Surgery Society (BOMSS) advises lifelong biochemical monitoring, with vitamin D 2,000–4,000 IU/day to maintain serum 25OHD >75 nmol/l, plus calcium replacement¹. Cortical bone, particularly at the forearm, is vulnerable, with SHPT-related loss associated with higher fracture risk².

Case Report: We present a 66-year-old woman who underwent laparoscopic gastric bypass in 1998 and was referred with persistently elevated PTH. She had longstanding vitamin D deficiency for many years before her dose of vitamin D3 was increased to 3,000 IU/day. Although this achieved repletion of Vitamin D, PTH remained elevated at 17.0 pmol/l (reference 1.3–9.3), with normal adjusted calcium (2.38 mmol/l) and stable renal function. Dual-energy X-ray absorptiometry (DEXA) showed osteopenia at the spine (T-score −1.2) and hip (−1.3), and osteoporosis at the distal forearm (−3.3), consistent with SHPT-related cortical bone loss. She was commenced on calcium and a bariatric-specific multivitamin. Repeat DEXA is planned in three years with ongoing biochemical monitoring.

Conclusion: This case shows that SHPT can arise decades after gastric bypass typically affecting cortical bone at the forearm. It underscores the need for lifelong bariatric-specific supplementation and monitoring of calcium, vitamin D, PTH, and bone health, as recommended by BOMSS guidance.

References: 1. O’Kane, M., Parretti, H.M., Pinkney, J., Welbourn, R., Hughes, C.A., Mok, J., Walker, N., Thomas, D., Devin, J., Coulman, K.D. and Pinnock, G., 2020. British Obesity and Metabolic Surgery Society Guidelines on perioperative and postoperative biochemical monitoring and micronutrient replacement for patients undergoing bariatric surgery—2020 update. Obesity Reviews, 21(11), p.e13087. 2. Stein, E.M., Carrelli, A., Young, P., Bucovsky, M., Zhang, C., Schrope, B., Bessler, M., Zhou, B., Wang, J., Guo, X.E. and McMahon, D.J., 2013. Bariatric surgery results in cortical bone loss. The Journal of Clinical Endocrinology & Metabolism, 98(2), pp.541-549.