Puberty

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

• What is puberty?
• When does puberty occur?
• What determines when puberty begins?
• What are the physical changes of puberty?
• What other changes in the body occur during puberty?
• What are the medical concerns associated with normal puberty?
• What are medical conditions associated with early, or late, puberty?
• Puberty At A Glance

What is puberty?

Puberty is the time at which a growing boy or girl begins the process of sexual maturation. Puberty involves a series of physical stages or steps that lead to the achievement of fertility and the development of the so-called secondary sex characteristics, the physical features associated with adult males and females (such as the growth of pubic hair). While puberty involves a series of biological, or physical, transformations, the process can also have an effect on the psychosocial and emotional development of the adolescent.

When does puberty occur?

The onset of puberty varies among individuals. Puberty usually occurs in girls between the ages of 10 and 14, while in boys it generally occurs later, between the ages of 12 and 16. In some African American girls, puberty begins earlier, at about age 9, meaning that puberty occurs from ages 9 to 14.

Adolescent girls reach puberty today at earlier ages than were ever recorded previously. Nutritional and other environmental influences may be responsible for this change. For example, the average age of the onset of menstrual periods in girls was 15 in 1900. By the 1990s, this average had dropped to 12 and a half years of age.

What determines when puberty begins?

The timing of the onset of puberty is not completely understood and is likely determined by a number of factors. One theory proposes that reaching a critical weight or body composition may play a role in the onset of puberty. It has been proposed that the increase in childhood obesity may be related to the overall earlier onset of puberty in the general population in recent years.

Leptin, a hormone produced by fat cells (adipocytes) in the body, has been suggested as a possible mediator of the timing of puberty. In studies, animals deficient in leptin did not undergo puberty, but puberty began when leptin was administered to the animals. Further, girls with higher concentrations of the hormone leptin are known to have an increased percentage of body fat and an earlier onset of puberty than girls with lower levels of leptin. The concentration of leptin in the blood is known to increase just before puberty in both boys and girls.

Leptin likely is one of multiple influences on the hypothalamus, an area of the brain that releases a hormone known as gonadotropin-releasing hormone (GnRH), which in turn signals the pituitary gland to release leutinizing hormone (LH) and follicle-stimulating hormone (FSH). LH and FSH secretion by the pituitary is responsible for sexual development.

A gene has been identified that appears to be critical for the normal development of puberty. The gene, known as GPR54, encodes a protein that appears to have an effect on the secretion of GnRH by the hypothalamus.

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