Why do periods stop?

Regular periods are generally a symptom of good health – a reassuring sign that everything is functioning as it should. It's no wonder then that many women become anxious when periods suddenly become erratic, or stop altogether.

Amenorrhoea is the medical term for the absence of periods. Primary amenorrhoea is the absence of periods by the age of 16, or the absence of periods two years after the development of secondary sexual characteristics. This is rare, and can be caused by structural abnormalities of the reproductive organs, chromosomal abnormalities, and gland disorders.

Secondary amenorrhoea, however, is more common. This is when a woman who previously had regular periods does not menstruate for at least three months, or when a woman with irregular periods does not menstruate for six to 12 months.

Here are some of the most common causes of secondary amenorrhoea:

  • Pregnancy
    If a fertilised egg is implanted in the uterus lining, menstruation ceases. Even after childbirth, periods may not resume whilst a woman is breastfeeding – this is called lactation amenorrhoea. Although the risk of pregnancy is reduced during this time, this is not a reliable contraceptive method.

    Ectopic pregnancies (when the foetus develops outside the womb) may also cause amenorrhoea.

  • Mental and emotional health
    In some cases, amenorrhoea is a symptom of a serious psychological problem. Severe stress or depression can alter the functioning of the hypothalamus and anterior pituitary gland – the areas of the brain that release hormones that regulate the menstrual cycle. This may temporarily prevent menstruation.

    A condition called pseudocyesis, when a woman convinces herself that she is pregnant, can also cause amenorrhoea.

  • Body weight and excessive exercise
    Amenorrhea is often associated with malnutrition, low body fat and excessive exercise. Eating disorders such as bulimia and anorexia nervosa can therefore result in erratic, or absent periods. This is because too few kilojoules are eaten, or too much energy is expended on exercise. Because not enough energy is available, menstruation ceases, and energy is conserved for basic life activities.

    Obesity is also associated with amenorrhoea, as excess fat cells can interfere with the process of ovulation.

  • Medication
    Amenorrhoea may be a side effect of certain medications, including sedatives, hormones, chemotherapy drugs, narcotics and antidepressants.

  • Hormonal imbalances
    Illnesses that affect the reproductive organs or hormones can result in amenorrhoea – this includes polycystic ovary syndrom (a hormonal disorder that causes high and sustained levels of oestrogen and androgen) and chlamydia (a sexually transmitted disease).

    Thyroid and pituitary disorders and tumours may also be to blame, as these glands produce hormones that affect the functioning of the menstrual cycle.

  • Contraceptives
    Extended cycle contraceptives such as Lybrel offer women the option of avoiding bleeding altogether. In other words, amenorrhoea can be purposefully induced.

    Moreover, it may take up to 12 months for regular ovulation and menstruation to resume after stopping oral contraceptives.

  • Perimenopause
    Perimenopause is the time period that leads up to menopause (the cessation of periods). During this period, the body begins to produce less oestrogen and progesterone. Fluctuating hormone levels cause ovulation to become erratic, and the menstrual cycle and intervals between periods become longer.

    These changes take place between two and eight years before a woman becomes fully menopausal.

  • Menopause
    When menstruation has not occurred for one year, menopause has officially set in. This is a natural part of the ageing process and the beginning of a new life phase. Any bleeding beyond this point could be a symptom of an underlying health problem.
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