Female Reproductive System

Female Sex Hormones and Puberty

Puberty, the maturation of genital organs, the development of secondary sexual characteristics, and the beginning of menstruation, begins with an increase of gonadotropin-releasing hormone (GnRH), which stimulates the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

Hormones of the female reproductive system control reproductive cycles and play important roles throughout the course of a woman's life. The physical changes during development follow characteristic patterns that are outlined by the Tanner scale. The Tanner stages of development are defined by changes to the appearance of breast tissue, pubic hair, axillary hair, and increase in height. Chronologically, puberty is the first major change in female growth and development that is controlled by hormones. Puberty typically begins between the ages of 10 and 11 and lasts until age 16 or 17. It is initiated by gonadotropin-releasing hormone (GnRH), which stimulates the production of follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

The first stage of puberty is thelarche, the beginning of breast development. This is considered Tanner stage II and also includes the beginning of long, downy hair growth of the labia in addition to peak growth velocity in height toward the end of this stage. Breast tissue softens and swells, and the shape and texture of the nipples and each areola (plural, areolae), the circular pigmented area of skin surrounding the nipples, may change. Breast development continues for another 18 to 24 months. Tanner stage III marks further enlargement of breast tissue and areolae, with no separation in their contours. In Tanner stage IV, the areola forms a secondary mound on top of the breast tissue. By Tanner stage V, the breast has fully matured and shows an adult single contour.

The second major change during puberty is the development of pubic hair, called pubarche. Downy hair growth begins on the labia in Tanner stage II, increases in amount and pigmentation in Tanner stages III and IV, and assumes an adult female distribution by Tanner stage V. Hair begins to grow on the labia, the flaps of skin that protect the clitoris, the vagina, and the urethral opening, as well as in the underarms. By the end of puberty, hair has spread across the pubic mound (the region above the groin) and may grow up the torso to the navel and down the upper regions of the thighs.

A landmark change that occurs during puberty is the onset of the first menstrual period, called menarche. Menarche generally occurs two to three years after thelarche at Tanner stage IV. The first menstrual period may or may not include ovulation, and the menstrual cycle may not be regular for as many as two years following menarche. Menarche typically occurs between ages 12 and 13, although it may begin as early as age 8 and as late as age 16 in normally developing girls.

Additional changes to the body are associated with puberty as well. These include general changes to body composition, such as an increase in body fat and changes in fat distribution. Body fat increases in the regions of the breasts, hips, thighs, upper arms, buttocks, and lower torso. In addition, the pelvis widens, creating a wider birth canal. Further, body odor may increase, and the voice may deepen, although this change is more pronounced in males than in females.

Stages of Puberty in Females

Many physical changes occur during puberty. The increase in hormones causes the body to increase in size and width. Additional changes specific to human females include the widening of the hips to accommodate childbirth, development of breast tissue, and formation of pubic hair in the groin region.