| Cellular studies |
1. Metformin is neither genotoxic nor cytotoxic and may potentially protect hyperglycemia-induced genomic instability in diabetic and non-diabetic adult male Wistar albino rats [54]. |
| 2. Metformin is not cytotoxic to Wistar rat Sertoli cells and can possibly be used safely in male diabetes patients of reproductive age [55]. |
| Animal studies |
1. Metformin increases the viability of pig sperms after 24 hours storage [56]. |
| 2. Metformin improves the quality of frozen-thawed dog semen during cryopreservation [57]. |
| 3. Metformin improves abnormalities in spermatogenesis and sperm motility in diabetic and non-diabetic male Wistar albino rats [54] and in diabetic male Sprague-Dawley rats [47]. |
| 4. Metformin limits testicular ischemia/reperfusion injury in male Wistar rats [58] and injury on sperm production in male Wistar albino rats [59]. |
| 5. Metformin reduces injury to the reproductive system induced by diabetes or obesity in rats [50,54,60]. |
| 6. Metformin improves fertility in obese male C57BL/6 mice [61,62]. |
| 7. Metformin has negative effects on sperm concentration, mobility and morphology in rabbits [46]. |
| 8. Metformin has a neutral effect on sperm viability and mobility in horses [63]. |
| Human studies |
1. An intervention trial conducted in Iraq: Metformin (850 mg bid for 12 weeks) may have a potentially harmful effect with regards to sperm count and activity [64]. |
| Author’s comments |
1. Metformin may protect against testicular injury and improve sperm quantity and quality in in rats or mice. However, this can not be proven in a human clinical trial. |
| 2. Metformin may theoretically exert beneficial effects on spermatogenesis through its improvement of inuslin resistance, weight reduction and metaboic control. However, more human research is needed. |
| 3. Interested readers may refer to review articles by Bertoldo et al [17], Ferreira et al [24], Faure et al [22], and Alzain et al [23]. |
