Background and aim: Polycystic ovary syndrome (PSOS) is a common disease of 
multifactorial etiology causing dangerous complications for women. The pathophysiology 
and intrinsic mechanisms underlying PCOS are complex and not fully determined. This study 
is designed to explore the mechanisms involved in PCOS in rats and to investigate the 
possible role of omega-3 in prevention of PCOS. Methods: 24 adult female albino rats were 
randomly classified into (1) Control groups (C): either non-treated (5 rats) or treated with 
the vehicle (3 rats), (2) Letrozole group (L): (8 rats), rats received letrozole orally (1mg/kg 
for 21 days) to induce PCOS and (3) Letrozole and omega-3 group (LO): (8 rats), in which 
PCOS was induced by letrozole and rats simultaneously received omega-3 (240 mg/kg orally) 
for 3 weeks. Histopathological examination of ovaries and biochemical analysis for serum 
was done. Results: In L group, ovaries showed features of polycystic ovary syndrome. The 
body weight, lipid peroxides, serum levels of insulin, testosterone, TNF-glucose, TGs, TC, 
and LDL were significantly increased associated with a significant decrease in serum HDL 
and FSH. In LO group the body weight, lipid peroxides and serum levels of insulin, 
testosterone, TNF-α, glucose, TGs, TC and LDL were significantly decreased associated with 
a significant increase in serum HDL. Microscopic examination of the ovaries revealed that 
LO group showed improvement of polycystic features. Conclusion: Administration of 
omega-3 led to improvement of PCOS as regard to the histopathological and biochemical 
changes most probably via its anti-oxidant and anti-inflammatory effects.