Puberty

Definition

Puberty is the period of human development during which physical growth and sexual maturation occurs.

Description

Beginning as early as age eight in girls--and two years later, on average, in boys--the hypothalamus (part of the brain) signals hormonal change that stimulates the pituitary. In turn, the pituitary releases its own hormones called gonadotrophins that stimulate the gonads and adrenals. From these glands come a flood of sex hormones--androgens and testosterone in the male, estrogens and progestins in the female--that regulate the growth and function of the sex organs. It is interesting to note that the gonadotrophins are the same for males and females, but the sex hormones they induce are different.

In the United States, the first sign of puberty occurs on average at age 11 in girls, with menstruation and fertility following about two years later. Boys lag behind by about two years. Puberty may not begin until age 16 in boys and continue in a desultory fashion on past age 20. In contrast to puberty, adolescence is more of a social/cultural term referring to the interval between childhood and adulthood.

Diagnosis

Puberty has been divided into five Sexual Maturity Rating (SMR) stages by two doctors, W. Marshall and J. M. Tanner. These ratings are often referred to as Tanner Stages 1-5. Staging is based on pubic hair growth, on male genital development, and female breast development. Staging helps determine whether development is normal for a given age. Both sexes also grow axillary (arm pit) hair and pimples. Males develop muscle mass, a deeper voice, and facial hair. Females redistribute body fat. Along with the maturing of the sex organs, there is a pronounced growth spurt averaging 3-4 in (8-10 cm) and culminating in full adult stature. Puberty can be precocious (early) or delayed. It all depends upon the sex hormones.

Puberty falling outside the age limits considered normal for any given population should prompt a search for the cause. As health and nutrition have improved over the past few generations, there has been a gradual decrease in the average age for the normal onset of puberty.

• Excess hormone stimulation is the cause for precocious puberty. It can come from the brain in the form of gonadotrophins or from the gonads and adrenals. Overproduction may be caused by functioning tumors or simple overactivity. Brain overproduction can also be the result of brain infections or injury.

• Likewise, delayed puberty is due to insufficient hormone. If the pituitary output is inadequate, so will be the output from the gonads and adrenals. On the other hand, a normal pituitary will overproduce if it senses there are not enough hormones in the circulation.

• There are several congenital disorders (polyglandular deficiency syndromes) that include failure of hormone output. These children do not experience normal puberty, but it may be induced by giving them the proper hormones at the proper time.

• Finally, there are in females abnormalities in hormone production that produce male characteristics--so called virilizing syndromes. Should one of these appear during adolescence, it will disturb the normal progress of puberty. Notice that virilizing requires abnormal hormones in the female, while feminizing results from absent hormones in the male. Each embryo starts out life as female. Male hormones transform it if they are present.

Delayed or precocious puberty requires measurement of the several hormones involved to determine which are lacking or which are in excess. There are blood tests for each one. If a tumor is suspected, imaging of the suspect organ needs to be done with x rays, computed tomography scans (CT scans), or magnetic resonance imaging (MRI).

Treatment

Puberty is a period of great stress, both physically and emotionally. The psychological changes and challenges of puberty are made infinitely greater if its timing is off.

In precocious puberty, the offending gland or tumor may require surgical attention, although there are several drugs now that counteract hormone effects. If delayed, puberty can be stimulated with the correct hormones. Treatment should not be delayed because necessary bone growth is also affected.

Prognosis

Properly administered hormones can restore the normal growth pattern.

Key Terms

Adrenals

Glands on top of the kidneys that produce four different types of hormones.

Computed tomography scan (CT)

A method of creating images of internal organs using x rays.

Embryo

The life in the womb during the first two months.

Hormone

A chemical produced in one place that has an effect somewhere else in the body.

Hypothalamus

Part of the brain located deep in the center of the skull and just above the pituitary.

Gonads

Glands that make sex hormones and reproductive cells--testes in the male, ovaries in the female.

Magnetic resonance imaging (MRI)

A method of creating images of internal organs. Magnetic resonance imaging (MRI) uses magnet fields and radio-frequency signals.

Pituitary

The "master gland" of the body, controlling many of the others by releasing stimulating hormones.

Syndrome

A collection of abnormalities that occur often enough to suggest they have a common cause.

For Your Information

Books

• Current Medical Diagnosis and Treatment, 1996. 35th ed. Ed. Stephen McPhee, et al. Stamford: Appleton & Lange, 1995.

• Harrison's Principles of Internal Medicine. Ed. Anthony S. Fauci, et al. New York: McGraw-Hill, 1997.

• Matsumoto, Alvin M. "The Testis." In Cecil Textbook of Medicine, Ed. J. Claude Bennett and Fred Plum. Philadelphia: W. B. Saunders Co., 1996.

• Nelson Textbook of Pediatrics. Ed. Richard E. Behrman. Philadelphia: W. B. Saunders Co., 1996.

• Rebar, Robert W. "The Ovaries." In Cecil Textbook of Medicine, Ed. J. Claude Bennett and Fred Plum. Philadelphia: W. B. Saunders Co., 1996.

Source: Gale Encyclopedia of Medicine, Published December, 2002 by the Gale Group

The Essay Author is J. Ricker Polsdorfer MD.

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