Evaluation of bone disease in morbidly obese women after gastric bypass and risk factors implicated in bone loss.

BACKGROUND: In patients undergoing gastric bypass, massive weight loss and impairment of calcium intake and absorption in the duodenum and proximal jejunum may increase the risk of bone mass loss and fractures. However, few data are available regarding the impact of this surgery on the skeleton. The aim of our study was to examine the skeletal changes in a cohort of morbidly obese Caucasian women during the first year after gastric bypass and to analyse the factors implicated in the development of bone loss.

METHODS: Sixty-two morbidly obese white women aged 45.3 +/- 8.9 years were studied. Anthropometric measurements, bone mineral density (BMD) screening using dual-energy X- ray absorptiometry and plasma determinations of calcium, phosphorus, parathyroid hormone (PTH), 25-hydroxyvitamin D [25(OH) D(3)] and insulin-like growth factor-I (IGF-I) were made prior to and 12 months after surgery.

RESULTS: A year after surgery, BMD significantly decreased at the femoral neck (10.2 +/- 5.7%) and at the lumbar spine (3.2 +/- 4.4%). In the follow-up, 16.1% of women had osteopenia at the femoral neck and 19.3% at the lumbar spine, and 1.6% developed osteoporosis at the lumbar spine. Patients with bone disease were significantly older; the percentage of women with menopause was greater in this group and had lower initial and final values of lean mass. However, no differences in body mass index, weight loss, fat mass, calcium, PTH, 25(OH) D(3) or IGF-I values were found between groups. In the logistic regression analysis, lean mass 12 months after surgery and menopause were found to be the main determinants of osteopenia after adjusting for age with odds ratios of 0.82 and 9.13, respectively.

CONCLUSIONS: There is a significant BMD loss at the femoral neck and lumbar spine a year after gastric bypass. Menopausal patients and those with greater lean mass loss are at greater risk and, consequently, should be closely followed up with periodic densitometries.