Robert Mathis of the Indianapolis Colts has been suspended by the NFL for the first four games of the season and fined $ 705,000 for testing positive for Clomid, a fertility drug which is banned by the NFL because of its properties that enhance athlete performance.

The six-time time Pro Bowl member explains that he was taking taking the substance as a fertility drug to conceive another child and presently, Mathis' wife is pregnant, reports ABC News.

Clomid is FDA approved for women only, not for men. As a fertility drug, it assists men who are dealing with low sperm count but it can also be used as a performance-enhancing substance commonly used by male athletes as it lowers sperm count and enhances an athlete's performance.

"Clomid is banned by the NFL because it can be used as part of a steroid cycle, reducing or eliminating side effects of their use and restoring the natural production of testosterone," recalls IndyStar.com.

Clomid as a treatment of male infertility has been used to address low sperm count to stimulate sperm production but has been used as a performance-enhancement drug as it raises one's testosterone levels.

Typically men with low sperm counts or low motility have lower levels of testosterone, the primary male hormone. Clomid (Clomiphene) works the same way for men and women. It binds receptors in the brain (specifically the hypothalamus and the pituitary gland) to increase the production of follicle stimulating hormone (FSH) and luteinizing hormone (LH). In men, the increase in FSH leads to an increase in sperm production, whereas the increase in LH leads to an increase in testosterone production, explains TFC.

According to the NFL's statement on the case, "Mr. Mathis tested positive is not approved by the FDA for fertility in males and is a performance-enhancing drug that has been prohibited for years," says the League. "Importantly, Mr. Mathis did not consult with the policy's Independent Administrator, a physician jointly approved by the NFL and NFL Players Association. Nor did he consult with his team doctor, the team's training staff, the NFLPA, the league office or the hotline established under the policy to give confidential information to players."