Puberty is the time in life when a person becomes sexually mature. It is a physical change that usually happens between ages 10 and 14 for girls and ages 12 and 16 for boys. Some African American girls start puberty earlier than white girls, making their age range for puberty 9 to 14.
Puberty starts when a part of the brain called the hypothalmus begins releasing a hormone called gonadotropin releasing hormone (GnRH). GnRH then signals the pituitary gland to release two more hormones - luteinizing hormone (LH) and follicle-stimulating hormone (FSH) – to start sexual development.
A study funded in part by NICHD has identified a gene that appears to be the crucial signal for the beginning of puberty. Without a functioning copy of the gene, known as GPR54, humans appear unable to enter puberty normally.