Relax the muscles around the anus making anal sex easier. Don't forget the condoms and other precautions if you are having anal sex, use extra strong condoms and plenty of water-based lubricant. As they interact with the body's own hormones they can have complex effects on sexual functioning. In men they can initially increase sex drive but continued use can have the opposite effect. There have also been reports of aggression and sexual violence by men taking large doses.
Women often report increased sex drive and irregular periods.
I've never looked'.