MARCO DE PRESENTACIÓN DE INFORMES

Although humans are fully sexually diff erentiated at birth, the diff erences between males and females are accentuated at puberty, the period during which the reproductive system matures, secondary sex characteristics develop, and the bod- ies of males and females begin to appear more distinctive. Th e changes of puberty are induced by testosterone in the male and estrogen and progesterone in the female.

Puberty in Females Th e fi rst sign of puberty in girls is breast development, followed by a rounding of the hips and buttocks. As the breasts develop, hair appears in the pubic region and later in the underarms. Shortly after the onset of breast development, girls show an increase in growth rate. Breast development usually begins between ages 8 and 13, and the time of rapid body growth occurs between ages 9 and 15.

The Menstrual Cycle A major landmark of puberty for young women is the onset of the me n strual cycle, the monthly ovarian cycle that leads to menstruation (loss of blood and tissue lining the uterus) in the absence of preg- nancy. Th e timing of menarche (the fi rst menstrual period ) varies with several factors, including ethnicity, genetics, and nutritional status. Th e current average age of menarche in the United States is around 12 and a half years of age, but menstruation may also normally start several years earlier or later.

Th e day of the onset of bleeding is considered to be day 1 of the menstrual cycle. For the purposes of our discussion, a cycle of 28 days will be used; however, normal cycles vary in length from 21 to 35 days. Th e menstrual cycle consists of the following four phases.

1. MENSES During menses, characterized by the menstrual

fl ow, blood levels of hormones from the ovaries and the pituitary gland are relatively low. Th is phase of the cycle usu- ally lasts from day 1 to about day 5.

2. ESTROGENIC PHASE Th e estrogenic phase begins when the

menstrual fl ow ceases and the pituitary gland begins to pro- duce increasing amounts of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Under the infl uence of FSH, an egg-containing ovarian follicle begins to mature, producing increasingly higher amounts of estrogen. Stimu- lated by estrogen, the e n dometrium ( the uterine lining) thickens with large numbers of blood vessels and uterine glands.

3. OVULATION A surge of a potent estrogen called estradiol

from the follicle causes the pituitary to release a large burst of LH and a smaller amount of FSH. Th e high concentration of LH stimulates the developing follicle to release its ovum. Th is event is known as ovulation. After ovulation, the follicle is transformed into the corpus luteum, which produces pro- gesterone and estrogen.

Ovulation theoretically occurs about 14 days prior to the onset of menstrual fl ow, with the window of greatest fertility occurring from a few days before ovulation to about one day after. Th is information has been used to attempt to predict the

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What are your personal views on circumcision? Who or what has infl uenced those opinions? Are the bases of your views primarily cultural, moral, or medical?

testosterone The most important male sex hormone; stimulates an embryo to develop into a male

and induces the development of male secondary sex characteristics during puberty.

puberty The period of biological maturation during

adolescence; in this stage of development, the individual becomes capable of sexual reproduction.

progesterone The most important female sex hormone; regulates the menstrual cycle and sustains pregnancy.

menstrual cycle The monthly ovarian cycle, regulated by hormones; in the absence of pregnancy, menstruation occurs.

menarche The fi rst menstrual period, experienced by most young women at some point during adolescence.

menses The portion of the menstrual cycle characterized by menstrual fl ow.

follicle A saclike structure within the ovary, in which an egg (ovum) matures.

endometrium The lining of the uterus.

ovulation The release of a mature egg (ovum) from an ovary.

corpus luteum The part of the ovarian follicle left after ovulation, which secretes estrogen and progesterone during the second half of the menstrual cycle.

common, PMS aff ects about 1 in 5 women, and PMDD af- fects fewer than 1 in 10 women.

Symptoms associated with PMS and PMDD can include breast tenderness, water retention (bloating), headache, fatigue, insomnia or excessive sleep, appetite changes, food cravings, ir- ritability, anger, increased interpersonal confl ict, depression, anxiety, tearfulness, inability to concentrate, social withdrawal, and the sense of being out of control or overwhelmed.

Despite many research studies, the causes of PMS and PMDD are still unknown, and it is unclear why some women are more vulnerable than others. Most researchers feel that PMS is probably caused by a combination of hormonal, neu- rological, genetic, dietary, and psychological factors.

Th e following strategies provide relief for many women with premenstrual symptoms, and all of them can contribute to a healthy lifestyle at any time:

• Limit salt intake. Salt promotes water retention and bloating.

• Exercise. Women who exercise may experience fewer symptoms before and after menstrual periods.

• _{Don’t use alcohol or tobacco. Alcohol and} tobacco may aggravate certain symptoms of PMS and PMDD.

• _{Eat a nutritious diet. Choose a low-fat} diet rich in complex carbohydrates from vegetables, fruits, and whole-grain breads, cereals, and pasta. Get enough calcium from calcium-rich foods and, if needed, supplements. Minimize your intake of sugar and caff eine, and avoid chocolate, which is rich in both. • _{Relax. Stress reduction is always benefi -}

cial, and stressful events can trigger PMS symptoms. Try relaxation tech- niques during the premenstrual time. If you’re a female with persistent premenstrual symptoms, keep a daily diary to track the types of symptoms, their sever- ity, and how they correlate with your menstrual cycle. See your physician for an evaluation and to learn about treat- ments that are available only by prescription.

Selective serotonin reuptake inhibitors (SSRIs), such as Prozac and Zoloft, are often used to treat PMS and PMDD. most fertile time during the menstrual cycle for fertility treat-

ments and natural family planning methods. However, a re- cent study showed that even women with regular menstrual cycles often have unpredictable ovulation, and can actually be fertile on any day of the month, including during menstrua- tion. Th e “window of fertility” is especially unpredictable in teenagers and women who are approaching menopause.

4. PROGESTATIONAL PHASE During the progestational phase

of the cycle, the amount of progesterone secreted from the corpus luteum increases and remains high until the onset of the next menses. Under the infl uence of estrogen and proges- terone, the endometrium continues to develop, readying itself to receive and nourish a fertilized ovum. When pregnancy occurs, the fertilized egg produces the hormone human cho- rionic gonadotropin (HCG), which maintains the corpus luteum. Th us levels of ovarian hormones remain high and the uterine lining is preserved, preventing menses.

If pregnancy does not occur, the corpus luteum degener- ates, and estrogen and progesterone levels gradually fall. Be- low certain hormonal levels, the endometrium can no longer be maintained, and it begins to slough off ,

initiating menses. As the levels of ovarian hormones fall, a slight rise in LH and FSH occurs, and a new menstrual cycle begins.

Menstrual Problems Menstruation is a normal biological process, but physical and/or emotional symptoms associated with the menstrual cycle are very common. Many women experience menstrual cramps, the severity of which tends to vary from cy- cle to cycle. Dysmenorrhea , discomfort as- sociated with menstruation, can include any combination of the following symptoms: lower abdominal cramps, backache, vomit-

ing, nausea, bloating, diarrhea, headache, and fatigue. Many of these symptoms can be attributed to uterine muscular con- tractions caused by chemicals called prostaglandins . Nonste- roidal anti-infl ammatory drugs (NSAIDs) such as ibuprofen (Motrin, Advil) block the eff ects of prostaglandins and are often eff ective in relieving dysmenorrhea. Oral contraceptives are also eff ective in reducing dysmenorrheal symptoms in most women.

Many women experience transient emotional symptoms prior to the onset of their menstrual fl ow. Depending on their severity, these symptoms may be categorized along a continuum: pr e menstrual tension, premenstrual syndrome (PMS), and premenstrual dysphoric disorder (PMDD). Premenstrual tension symptoms are mild and may include negative mood changes and physical symptoms such as ab- dominal cramping and backache. More severe symptoms are classifi ed as PMS; very severe symptoms that impair normal daily and social functioning are classifi ed as PMDD. All three conditions share a defi nite pattern. Symptoms appear prior to the onset of menses and disappear within a few days after the start of menstruation. Premenstrual tension is quite

dysmenorrhea Painful or problematic menstruation.

premenstrual tension Mild physical and emotional changes associated with the time before the onset of menses.

premenstrual syndrome (PMS) A disorder characterized by physical discomfort, psychological distress, and behavioral changes that begin after ovulation and cease when menstruation begins.

premenstrual dysphoric disorder (PMDD) A severe form of PMS, characterized by symptoms serious enough to interfere with daily activities and relationships.

t e r m s

75% of women

experience

premenstrual

symptoms during

their childbearing

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H O R M O N E S A N D T H E R E P R O D U C T I V E L I F E C Y C L E 91 greater in males than in females. By adulthood, men on aver- age have one and a half times the lean body mass of women, and only about half the body fat.