We aimed to investigate serum antioxidant enzymes and nitric oxide (NO) levels in postmenopausal women with osteoporosis (OP) and in healthy controls; and to determine the relationship between these enzymes, NO and clinical parameters in this present study.

Forty-five postmenopausal women fulfilling OP diagnostic criteria of World Health Organization (WHO) and 42 postmenopausal healthy women without OP were enrolled. Patients in the study population were selected among individuals that were not pre-diagnosed or pre-treated for OP. Patients with metabolic bone diseases, fracture history, which were smokers, alcohol users and taking antioxidant drug treatment, were excluded from the study. Dual Energy X-ray Absorptiometry (DXA) results, body mass indices and demographic data were recorded. Erythrocyte catalases (CAT), glutathione reductase (GR) enzyme activities and erythrocyte glutathione (GSH) levels, plasma malondialdehyde (MDA) levels were measured by spectrophotometer whereas plasma nitrite+nitrate (NOx) levels were measured by ELISA microplate-reader.

Patients had significantly lower GR (P<0.01) enzyme activity and higher levels of MDA (P<0.01) and NO (P<0.01) than non osteoporotic healthy controls. There was no significant difference between both groups in erythrocyte GSH levels and CAT activities. Total femoral BMD measurements significantly correlated with MDA levels (P=0.001). There was no significant relationship between other antioxidants and lumbar or femoral BMD.

Oxidative stress may play an important role in postmenopausal bone loss and therefore it might be considered when pathogenesis of postmenopausal OP has been investigated.