The objective of this study is to assess changes bone mineral density and bone metabolism after laparoscopic Roux-en-Y gastric bypass surgery. The investigators hypothesize that weight loss after laparoscopic Roux-en-Y gastric bypass surgery will be associated with increased bone turnover, changes in bone metabolism, and loss of bone mass.

Obesity is an increasing problem within the United States. Fifteen million people in the United States are considered morbidly obese, with a body mass index (BMI) greater than 40 kg/m2. A wealth of literature has shown laparoscopic Roux-en Y gastric bypass surgery to be an effective procedure to reduce excess body weight. But a paucity of research examines the effects of laparoscopic Roux-en Y surgery on the skeleton.

Bone remodeling is a complex process involving bone resorption and formation-a process dependent upon local and systemic influences. Obesity is one of these influences that is poorly understood. Obesity is associated with a reduced risk of osteoporosis. Obesity may be protective due to increased weight bearing, increased production of estrogen by adipose tissue, or increased bone formation due to higher levels of insulin.

It is known that weight loss in healthy individuals is associated with bone loss. Several small studies have reported bone loss in patients undergoing vertical band gastroplasty or jejunoileal bypass weight loss surgeries. Other reported metabolic disease disarrangements following weight loss surgery are decreased serum calcium, decreased serum 25-hydroxy vitamin D, and hyperparathyroidism.

In the bariatric literature, weight loss has been associated with an increased risk of bone mineral loss and fracture. Osteoporosis has been described in patients who lost weight after jejunoileal bypass surgery. Premenopausal women appeared to be spared from bone mineral loss, thus indicating a protective effect from the premenopausal state. Bone mineral loss is seen both in premenopausal women and in men after weight loss surgery.

Roux-en Y gastric bypass has been shown to be more effective at weight loss than has the adjustable silicone gastric band. It has also been linked with increased loss of bone mineral density. Another study found an increase in bone turnover as well as a decrease in total bone mass and trochanteric bone density in laparoscopic Roux-en Y gastric bypass patients.

Previous research at our institution has shown a statistically significant increase in the prevalence of hyperparathyroidism in post-gastric bypass patients. However, our previous research did not examine the impact that these hormonal changes impart upon bone density. We have found a statistically significant incidence of vitamin D deficiency in our patients following this surgery. We intend to expand upon our own research as well as that of others by exploring the associations between the development of hyperparathyroidism, bone metabolic derangements, weight loss, and bone density.

Inclusion Criteria:

• Morbidly obese female patients undergoing elective laparoscopic Roux-en-Y gastric bypass at a single institution

Exclusion Criteria:

• Male patients
• Patients unable to fulfill the study protocol requirements

Study population will consist of patients undergoing laparoscopic gastric bypass at a community-based teaching institution