Boys generally reach their adult height by age 17 or 18, but we've all known young men who continued growing during the college years. Testosterone also stimulates muscular development in the growing boy, as well as the bone growth that results in increased height. The adolescent weight spurt in the boy occurs at about the same time as the height spurt. A good deal of that weight is muscle and bone. A boy's weight increases from about 85 pounds at the beginning of puberty to an adult weight of 150 pounds or more by age 18.
Androgens are also responsible for other changes in the genitals of boys.
The penis grows in length and then later in width, usually about a year before the boy reaches his peak growth rate. The developing testes produce sperm and semen relatively early in adolescence. Pubic and underarm hair develops soon after genital growth, along with the maturation of skin glands. Boys may be disturbed about the acne but reluctant to request help in managing it. New medications can be a big help.