Puberty

Definition

Puberty is the maturation of sexual characteristics. It is the physical changes that occur between ages 10 and 14 for girls and ages 12 and 16 for boys.

Causes of Puberty

Normal puberty starts when a part of the brain called the hypothalmus releases a hormone called gonadotropin-releasing hormone (GnRH). GnRH signals the pituitary gland (a pea-sized gland near the base of the brain) to release two more hormones: luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

It is these hormones that travel to different sites in the body to increase the production of sex hormones. LH and FSH signal the ovaries in girls to produce estrogen. In boys, LH and FSH signal the testes to make androgen (male) hormones. These hormones then signal the child’s body to go through the physical changes of puberty. The normal sequence of hormonal stimulation that causes puberty are:

• Hypothalamus (GnRH) -->
  • Pituitary (LH & FSH) -->
    • Ovaries or Testes (Estrogen or Testosterone) -->
      • Cause secondary sex characteristics (breast growth, pubic hair and menses in girls; penis and testes growth, and pubic and body hair growth in boys)

Signs of puberty

In general, the puberty signs are:

• In girls: The first sign of puberty is usually breast development. Other signs are the growth of hair in the pubic area and armpits, and acne. Menstruation (or a period) occurs last.

• In boys: Puberty usually begins with the testicles and penis getting bigger. Then hair grows in the pubic area and armpits. Muscles grow, the voice deepens, and acne and facial hair develop as puberty continues.

• Both boys and girls undergo a Growth Spurt in Height.

Both boys and girls usually have a growth spurt (a rapid increase in height) that lasts for about 2 or 3 years along with the signs listed above. This brings them closer to their adult height, which they reach after puberty.

The Tanner Five Stages of Puberty

Physicians report five “Tanner Stages” for puberty in both boys and girls. This five stage system was established by Drs. Tanner and Marshall in 1962. It describes characteristic changes that normally take place in a particular sequence.

Puberty most often happens in the following order. However, it is very normal for a child to start the stages with variations in the order.

Girls most often begin puberty with breast buds and bone growth causing a growth spurt in height. Next, girls start to get pubic hair and underarm hair. Menarche, or the first menstrual period, usually happens next. Although this is the typical sequence of changes, it is normal to have some of the steps happen in a different order.

In boys, puberty usually starts with an increase in size of the testicles. Next, the boy grows pubic hair and the penis becomes larger. Sperm is able to be produced at this stage. Growth of the bones (causing a growth spurt in height) and growth in muscle mass usually happen last.

Sexual Development of Girls

Girls usually start to show the physical changes of puberty between the ages of 9 and 13, which is slightly sooner than boys. The female sex hormone called estrogen and other hormones cause the physical changes. Many girls are fully developed by the age of 16. Some girls will continue to develop through age 18.

The Five Stages of Sexual Development of Girls (in detail):

• Stage 1: Between ages 8 to 12 .
  • No visible signs of physical development. But the ovaries are enlarging and hormone production is beginning.

• Stage 2: May begin anywhere from ages 8 to 14.
  • Height and weight increase rapidly.
  • Fine hair growth begins close to the pubic area and underarms.
  • Breast buds appear; nipples become raised and this area may be tender.
  • Sweat and oil glands become more active which can result in acne.

• Stage 3: May begin anywhere from ages 9 to 15.
  • Breasts become rounder and fuller.
  • Hips may start to widen in relation to waist.
  • Vagina begins secreting a clear or whitish fluid.
  • Pubic hair becomes darker, thicker, and curlier.
  • Height and weight continue to increase.
  • For some girls, ovulation and menstruation (periods) begin, but may be irregular.

• Stage 4: May begin anywhere from ages 10 to 16.
  • Underarm hair becomes darker.
  • Pubic hair starts to form a triangular patch in front and around sides of genital area.
  • The nipple and the dark area around the breast (areola) may stick out from the rest of the breast.
  • For many girls, ovulation and menstruation (periods) begin, but may be irregular.

• Stage 5: May begin anywhere from ages 12 to 19.
  • Adult height is probably reached.
  • Breast development is complete.
  • Pubic hair forms a thick, curly, triangular patch.
  • Ovulation and menstruation (periods) usually occur regularly.
  • Overall look is that of a young adult woman.

Drawings of Female Genitalia Development

Drawings of Female Breast Development

Drawings of both Male and Female Sexual Development in the Tanner Stages

Sexual Development of Boys

Boys usually start to show the physical changes of puberty between the ages of 11 and 14, which is slightly older than when girls start puberty. The male sex hormone called testosterone and other hormones cause the physical changes.

Here are the five stages and what happens:

• Stage 1: May begin as early as age 9 and continue until 14.
  • No sign of physical development but hormone production is beginning.

• Stage 2: May begin anywhere from ages 11 to 13.
  • Height and weight increase rapidly.
  • Testicles become larger and scrotum hangs lower.
  • Scrotum becomes darker in color.
  • Fine hair growth begins at the base of the penis.
  • Hair growth may begin on the legs and underarms.

• Stage 3: May begin anywhere from ages 12 to 14.
  • The penis, scrotum, and testicles grow.
  • Pubic hair becomes darker, thicker, and curlier.
  • Muscles become larger and shoulders become broader.
  • Sweat and oil glands become more active, which can result in acne.
  • Sperm production may begin.
  • Temporary swelling and tenderness may occur around nipples.
  • Height and weight continue to increase.
  • Hair growth on the legs and underarms continues.

• Stage 4: May begin anywhere from ages 13 to 16.
  • Sperm production has usually begun.
  • The larynx (Adam's apple) increases in size. Vocal chords become longer and thicker, and the voice begins to break or crack, then becomes low.
  • Height and weight continue to increase.
  • Penis and testicles continue to grow.
  • Pubic hair increases in amount and becomes darker, coarser, and curly.

• Stage 5: May begin anywhere from ages 14 to 18.
  • Growth of facial hair begins.
  • Chest hair growth may begin (not all males get much chest hair).
  • Adult height is reached.
  • Penis and testicles have reached full adult size.
  • Pubic, underarm, and leg hair are adult color, texture, and distribution.
  • Overall look is that of a young adult man.

Drawings of both Male and Female Sexual Development in the Tanner Stages

Variations in the sequence of puberty

Puberty most often happens in a certain order. However, it is very normal for a child to start the stages with variations in the order.

Abnormalities in the timing of puberty:

• Some children may begin puberty earlier than normal, a condition called Precocious Puberty. If signs of puberty occur early (before age 7 or 8 for girls and before age 9 for boys), it is a good idea for parents and caregivers to talk to their pediatrician to see if treatment is needed.

• Other children may have delayed puberty, meaning the process begins later than normal. Sometimes there is a reason for puberty starting late. Low body fat will delay puberty in girls. For example, many young girls who are gymnasts start puberty later than non-gymnasts. However, in many cases, there is no known reason for the delay.

If development is later than normal, it may be a good idea for parents and caregivers should talk to a health care provider, who can make sure there is not a medical condition causing the delay. Fortunately, most children with delayed puberty need no treatment and begin puberty on their own body’s time.

References

U.S. Department of Health & Human Services: Sexual and Reproductive Development

Disorders of Puberty RD Blondell, M.D., MB Foster, M.D., and KC Dave, M.B.B.S. American Family Physician July 1, 1999.

External Links

For Tweens and Teens:

American Academy of Pediatrics Teen Q&A

American Academy of Family Physicians. Kids Health. Growing Up- Links to Kids’ Questions on Puberty

The Nemours Foundation: Everything You Wanted to Know About Puberty

American College of Obstetricians and Gynecologists ACOG: Growing Up. ACOG Patient Education Pamphlet

American College of Obstetricians and Gynecologists ACOG: You and Your Sexuality. ACOG Teen Education Pamphlet

Important References:

The Nemours Foundation: The Female Reproductive System

The Nemours Foundation: The Male Reproductive System

Medline Plus: Teen Development

For Parents:

American Academy of Family Physicians When Your Child Is Close to Puberty

U.S. Department of Health & Human Services: Sexual and Reproductive Development

Nemours Foundation: Growth and Your 13-to 18-Year-Old

American Academy of Family Physicians: What to Expect When Your Child Goes Through Puberty