Physiological Amenorrhea

Physiological amenorrhoea (lack of periods) is normal during certain times in a woman's life.

Before Puberty

Amenorrhoea is normal in childhood before the onset of puberty. All women are born with a set number of eggs in their ovaries which are genetically determined. This number ranges between two million to three million.

The number of eggs degenerate and gradually decrease in number until by the time a girl reaches her first period at about the age of eleven years, she has only about 300,000 oocytes in her ovaries. Of these only about 500 oocytes are destined to develop into mature follicles during the girl's reproductive life.

Before puberty, the pituitary gland in the brain is mainly concerned with ensuring physical growth. The cue to start the periods comes from an area of the brain called the hypothalamus. As the girl reaches 9 - 10 years, the hypothalamus starts to secrete a special hormone called the Gonadotrophin Releasing hormone (GnRH). The GnRH stimulates the pituitary gland to secrete hormones called Follicle Stimulating Hormones (FSH) and Leutinizing Hormones (LH).

The FSH and LH stimulate the ovaries to release an ovum ('ovulation') every month. While most girls get their menstrual periods regularly every month once menstruation starts, regular periods may not be established till the age of 16 -18 years in other healthy and normal girls.

During Adolescence

Occasional loss of periods lasting for 2 – 3 months is normal during the teen years, especially in the early adolescence. It takes some time for the pituitary to secrete GnRH regularly. The ovaries may also need time to settle into a routine of ovulation and regular cyclical periods. Amenorrhea occurs in 10-20% of girls in their teens with no lasting side effects and no future problems with fertility.

During Pregnancy

Missing a period is one of the earliest and most reliable symptom of pregnancy. It is also the commonest cause of amenorrhea in adult women in the reproductive age.

During pregnancy, large amounts of oestrogen and progestogen are secreted from the chorion in early pregnancy and from the placenta after the third month. This high levels of estrogen and progesterone suppresses the secretion of FSH and LH from the pituitary gland. Since ovulation cannot occur unless the ovaries are stimulated by FSH and LH, periods also fail to occur.

While Breastfeeding

After childbirth, it becomes important for the body to nourish the baby. So the the pituitary gland concentrates on producing large amounts of the hormone Prolactin. Prolactin is the main hormone responsible for stimulating growth of the breasts during pregnancy and for initiating and maintaining the secretion of breastmilk while breastfeeding the baby. The high levels of prolactin suppresses the secretion of FSH and LH from the pituitary gland.

The blood level of Prolactin, which is already high during pregnancy, increases sharply after childbirth. If breastfeeding is started and continued, the level remains high, preventing ovulation and menstruation. If however, breastfeeding is never started or stopped at any time, the level of prolactin decreases. The pituitary starts to secrete FSH and LH, and the menstrual cycle begins to occur again.

During Menopause

No periods occur after the menopause. Menopause sets in during the ages of 45 to 55 years, the average being 51 years.

Menopause before the age of 40 years is rare and is called premature menopause. When the number of Graafian follicles in the ovary gets exhausted, the ovary fails to react to the circulating FSH and LH hormones secreted by the pituitary gland. As a result, the pituitary secretes more and more FSH in an attempt to stimulate the ovaries. The high levels of FSH and low levels of estrogen are the main diagnostic features of menopause.

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