Page 96 - 86 human physiology part-2

The Female Reproductive System

appear. Together with these symptoms, the woman may also have increasingly scanty and erratic
menstrual periods.

Technically, menopause refers to the cessation of menses; the gradual process through which this
occurs, which typically takes a year but may last as little as six months or more than five years, is
known as climacteric. A natural or physiological menopause is that which occurs as a part of a
woman's normal aging process. However, menopause can be surgically induced by such procedures as
hysterectomy.

The average onset of menopause is 50.5 years, but some women enter menopause at a younger
age, especially if they have suffered from cancer or another serious illness and undergone
chemotherapy. Premature menopause is defined as menopause occurring before the age of 40, and
occurs in 1% of women. Other causes of premature menopause include autoimmune disorders, thyroid
disease, and diabetes mellitus.

Premature menopause is diagnosed by measuring the levels of follicle stimulating hormone (FSH)
and luteinizing hormone (LH). The levels of these hormones will be higher if menopause has occurred.
Rates of premature menopause have been found to be significantly higher in both fraternal and
identical twins; approximately 5% of twins reach menopause before the age of 40. The reasons for this
are not completely understood. Post-menopausal women are at increased risk of osteoporosis.

Perimenopause refers to the time preceding menopause, during which the production of hormones
such as estrogen and progesterone diminish and become more irregular. During this period fertility
diminishes. Menopause is arbitrarily defined as a minimum of twelve months without menstruation.
Perimenopause can begin as early as age 35, although it usually begins much later. It can last for a few
months or for several years. The duration of perimenopause cannot be predicted in advance.

Premenstrual Syndrome (PMS) It is common for women to experience some discomfort in the
days leading up to their periods. PMS usually is at its worst the seven days before a period starts and
can continue through the end of the period. PMS includes both physical and emotional symptoms:
acne, bloating, fatigue, backaches, sore breasts, headaches, constipation, diarrhea, food cravings,
depression, irritability, difficulty concentrating or handling stress.

Ovarian and Uterine Cycles in the Nonpregnant Woman

Ovarian Cycle Events Uterine Cycle Events
Follicular phase - FSH secretion begins. Menstruation - Days Endometrium breaks down.
Days 1-13 2-5
Follicle maturation Proliferative phase - Endometrium rebuilds.
occurs. Days 6-13
Estrogen secretion is
prominent.
Ovulation - Day LH spike occurs.
14*
Luteal phase - Days LH secretion continues. Secretory phase - Days Endometrial thickens, and
15-28 15-28 glands are secretory.

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