Background: Although lipid peroxidation has been suggested to play a role in the etiology of many diseases, there is no report about its role in acromegaly in the literature. In the present study, we analyzed the basal levels of lipid peroxides (LPO) in newly diagnosed acromegalic patients, and to evaluate whether octreotide (OCT) has any effect on lipid peroxidation in these patients. Methods: Plasma lipid peroxide levels before and after acute OCT administration were measured in 12 newly diagnosed acromegalic patients. Blood samples were drawn at basal and 4, 8, and 24 h after octreotide injection (100 mug s.c.). Plasma concentrations of lipid peroxides were estimated from measurement of thiobarbituric acid reactive substance (TBARS), using 1,1,3,3-tetra-ethoxypropane as a standard. Results: This study shows that acromegalic patients have significantly higher basal plasma lipid peroxides levels compared to hours after OCT injection (p<0.001). Although a significant decrease was observed after 8 and 24 h in comparison to basal level (p<0.001), the lipid peroxide levels tended to increase at 24 h though still low when compared to basal level. Conclusion: Acromegalic patients have high basal lipid peroxide levels, which was significantly decreased after OCT administration. (C) 2003 Elsevier B.V. All rights reserved.