Methyl-1-testosterone is a prohormone used as a bodybuilding supplement. It is seven to 16 times more potent than regular testosterone. The chemical bonding of naturally occurring testosterone is manipulated to create the anabolic steroid 1-testosterone and then methylated to created methyl-1-testosterone to help prevent liver destruction and increase its oral availability. Methyl-1-testosterone is banned in the United States.

This substance has never been studied in a clinical trial, so it has no known pharmaceutical or medical applications. The only evidence as to its effectiveness is through the testimonies of its users within the bodybuilding community. It is considered just as potent as traditionally illegal steroids, and most users have reported an average gain of 10 pounds (4.5 kg) of muscle during two-week dosing cycles.

The body produces endogenous testosterone naturally. As the aging process begins in middle age, the body's natural testosterone production decreases. After the age of 30 is when the use of methyl-1-testosterone and other prohormones is most effective.

The main side effects of methyl-1-testosterone use are similar to those of other steroids, but because of its potency, the side effects generally are more severe. The side effects include mood irregularities, increased aggression, increased blood pressure, decreased appetite, sexual dysfunction, water retention, breast enlargement, male pattern baldness, a distended stomach and acne.

The main reason for these side effects is that methyl-1-testosterone will not convert to estrogen, so the body increases its natural production of estrogen to try to counteract the increased testosterone. When methyl-1-testosterone usage stops, the body usually will not reduce its estrogen production.

Methly-1-testosterone can be very destructive to the individual who takes it. Many users are unaware of the side effects or choose to ignore them. There are many legal bodybuilding substances, including creatine, that can be used in place of methyl-1-testosterone to achieve similar results with much less severe side effects.