Genetics play a role in low testosterone for some men, but underlying causes vary widely. Many genes influence testosterone ...

Numerous factors -- including body mass index (BMI), lifestyle, relationship status, and a number of disease states -- were tied with declining testosterone levels in men over 70, researchers found.

Some testosterone-boosting dietary supplements contain the amino acid D-aspartic acid. Some studies support that D-aspartic acid can increase testosterone production, but other studies refute this.