From MedlinePlus Genetics
Central precocious puberty is a condition that causes early sexual development in girls and boys. While puberty normally starts between ages 8 and 13 in girls and between ages 9 and 14 in boys, girls with central precocious puberty begin exhibiting signs before age 8, and boys with this disorder begin before age 9. Signs of puberty include development of pubic and underarm hair, a rapid increase in height (commonly referred to as a "growth spurt"), acne, and underarm odor. Girls also develop breasts and begin their menstrual periods. Boys have growth of the penis and testes and deepening of the voice. Because of the early growth spurt, children with central precocious puberty may be taller than their peers; however, they may stop growing abnormally early. Without proper treatment, some affected individuals are shorter in adulthood compared with other members of their family. Developing ahead of their peers can be emotionally difficult for affected individuals and may lead to psychological and behavioral problems.  https://medlineplus.gov/genetics/condition/central-precocious-puberty