Precocious puberty in boys is the premature onset of puberty, so that it begins before the age of 9 and one-half years. It is rare and affects only about 1 child in every 10,000 in the United States. Premature stimulation of the endocrine system releases hormones from the pituitary gland at the base of the brain. These hormones stimulate the testes to make sex hormones. The sex hormones, including testosterone, cause sexual maturation in boys.
Sex hormones accelerate growth and also control the skeletal process that ends growth.
Boys who start puberty prematurely are tall for their age, but growth stops earlier for them. Their full height potential as adults is never achieved. They often grow no taller than 60 to 65 inches. Behavioral changes occur during premature puberty. Some boys become more aggressive than their peers and develop a sex drive.