In males, testosterone is responsible for many normal functions, including growth and development of the genitals, muscles, and bones. It also helps cause normal sexual development (puberty) in boys. Methyltestosterone is similar to the natural testosterone produced by your body. It belongs to a class of drugs known as androgens. It works by affecting many body systems so that the body can develop and function normally.
 
Methyltestosterone may also be used in certain adolescent boys to cause puberty in those with delayed puberty.

Applications:
How to use methyltestosterone
You  need take this medication by mouth with or without food, usually 1 to 4 times a day.
Dosage is based on your medical condition, testosterone blood levels, and response to treatment.
Use this medication regularly in order to get the most benefit from it. To help you remember, take it at the same times each day.
Do not suddenly stop using methyltestosterone if you have been using it regularly for an extended time or if it has been used in high doses. In such cases, your body will no longer make its own testosterone, and withdrawal reactions (such as tiredness, weakness, depression) may occur.