Adults with obesity who underwent Roux-en-Y gastric bypass experienced high-turnover bone loss and bone microarchitectural deterioration that persisted 5 years after the procedure, according to findings published in The Journal of Clinical Endocrinology & Metabolism.

“[Roux-en-Y gastric bypass]-associated skeletal fragility is mediated by accelerated, high-turnover bone loss and has been documented in the short term in multiple longitudinal studies,” Katherine G. Lindeman, of the endocrine unit at Massachusetts General Hospital, Boston, and colleagues wrote in the study background. “Collectively, these studies document that a decline in bone density up to 10% is common in the initial 1-2 years after [Roux-en-Y gastric bypass]. [Roux-en-Y gastric bypass] also leads to short-term declines in volumetric bone density of the axial and peripheral skeleton and weakening of peripheral bone microarchitecture. However, the long-term skeletal consequences of [Roux-en-Y gastric bypass] have not been well-characterized beyond these initial postsurgical years.”

In an observational study, researchers assessed longitudinal data on 21 patients with obesity undergoing Roux-en-Y gastric bypass at an academic medical center.

DXA was used to measure spine and hip areal bone mineral density, and quantitative CT was used to measure trabecular volumetric BMD of the spine. In a subset of participants, high-resolution peripheral quantitative CT was used to measure volumetric BMD and microarchitecture of the distal radius and tibia.

At each study visit, the researchers also measured serum type 1 collagen C-terminal telopeptide (CTX), which assesses bone resorption, and procollagen type 1 N-terminal propeptide (P1NP), which evaluates bone formation, and assessed physical activity. Study participants were advised to maintain a calcium intake between 1,200 mg and 1,500 mg daily and a vitamin D intake of 3,000 IU daily throughout the study.

At 5 years, researchers observed a mean 7.8% decrease in areal BMD at the spine and a mean 15.3% decrease in areal BMD at the total hip. However, the pace of spine areal BMD reduction slowed over time, with most of the bone loss observed within the first 2 years, according to researchers.

At the femoral neck, areal BMD decreased by a mean of 14.1% at 5 years. Additionally, researchers observed a mean 12.1% decrease in trabecular spine volumetric BMD at 5 years (P ≤ .001).

Peripheral sites showed continued and stable decreases over 5 years, with parallel reductions in cortical and trabecular microarchitecture. This led to a 20% decrease in estimated failure load at the radius and a 13% decrease at the tibia (P < .001), the researchers wrote.

After Roux-en-Y gastric bypass, significant increases in bone turnover markers were seen. At 2 years postoperatively, serum CTX was 196% higher vs. baseline levels and remained 150% above baseline at 5 years (P < .001). Increases were also seen in serum P1NP, reaching the highest point at 63% at 3.5 years after surgery, and remaining 34% higher at 5 years (P = .017 for comparisons vs. baseline).

“We found that areal and volumetric bone density and skeletal microarchitecture continue to deteriorate through 5 years after [Roux-en-Y gastric bypass] surgery, leading to substantial, cumulative bone loss,” the researchers wrote. “Adults undergoing [Roux-en-Y gastric bypass] warrant close follow-up to detect changes in bone density as well as to prevent secondary hyperparathyroidism and promote physical activity.” – by Jennifer Byrne