LAUSR

Abstract Background Nowadays, polycystic ovary syndrome (PCOS) is a prevalent cause of infertility affecting women of reproductive age around the world. Thymoquinone is a natural antioxidant, derived from Nigella sativa. Objectives The current study aimed to evaluate the protective effects of thymoquinone on the detrimental effects of PCOS rats induced with letrozole. Methods Thirty‐two female rats were randomly divided into four groups: (1) Control, (2) PCOS, (3) PCOS+5 mg/kg thymoquinone and (4) PCOS+10 mg/kg thymoquinone. Thymoquinone was administered every 3 days for 30 days. Ovaries were histopathologically and stereologically examined, and antioxidant and apoptotic enzymes gene expression in ovaries and sex hormones in serum were measured. Results The number of unilaminar, multilaminar, antral, and graffian follicles, volume density of corpus luteum (p < 0.01), and GPx1 gene expression in ovaries and level of FSH in the blood increased in both thymoquinone groups when compared to untreated PCOS (p < 0.05). Ovaries in thymoquinone groups showed a significant reduction in the number of atretic follicles, ovary weight and volume, volume density of cortex and ovarian cysts, Bax gene expression (p < 0.01) and Bax/Bcl2 ratio as well as levels of luteinizing hormone (LH), LH/FSH ratio and testosterone (p < 0.05) in the blood of female rats when compared to PCOS group. Administration of thymoquinone restored the most detrimental effects of PCOS on ovaries (p < 0.01) and sexual hormones (p < 0.05) in rats. Conclusions These data suggest that thymoquinone has improved effects on ovarian function in the PCOS rat model. Therefore, thymoquinone might be useful as a protective agent and adjunct treatment in PCOS patients.