Objective: To assess the influence of weight reduction therapy on serum osteoprotegerin (OPG) concentration in obese patients and compare these results with normal-weight controls.
Research methods and procedures: Forty-three obese women (BMI, 36.7 +/- 4.1 kg/m2; mean age, 50.1 +/- 4.5 years) were studied. The control group consisted of 19 normal-weight women (BMI, 24.2 +/- 2.1 kg/m2; mean age, 53.8 +/- 5.2 years). In all patients, serum concentrations of OPG, C telopeptide of type I collagen containing the cross-linking site (CTX), osteocalcin, parathormone, 25-(OH)-D3 (vitamin D), and total calcium and phosphorus were assessed before and after a 3-month weight reduction therapy.
Results: In obese subjects, serum concentrations of OPG, 25-(OH)-D3, osteocalcin, total calcium, and phosphorus were significantly lower, and serum concentration of parathormone was significantly higher, before weight reduction therapy in comparison with normal-weight controls. After weight reduction, a significantly higher serum concentration of 25-(OH)-D3 and CTX and significantly lower concentration of OPG were found.
Discussion: Serum concentration of OPG was significantly lower in obese patients in comparison with normal-weight controls. Weight reduction therapy resulted in further decrease in OPG serum concentrations. Therefore, OPG cannot be treated as a protective factor from bone loss in obese patients.