One of the problems with starting puberty at an earlier age is that children also enter a period of rapid growth and weight gain during puberty. When puberty ends, growth stops. Kids with precocious puberty usually don't achieve their full adult height potential. If untreated, boys typically grow no taller than 5 feet 4 inches and girls rarely reach 5 feet.

Early puberty is usually thought of as being either central precocious puberty, which can be from a tumor of the central nervous system. However, most cases of early puberty, are idiopathic, meaning that no cause is found. The timing of puberty has a genetic component. A history of early puberty in a parent or sibling is relevant and decreases the likelihood that early puberty has an organic cause.