Abnormalities of Menstruation

Published on 10/03/2015 by admin

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Last modified 10/03/2015

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Chapter 6 Abnormalities of Menstruation

Normal and physiological changes in the menstrual cycle

Normal menstrual cycles have a length of 21–35 days (mean 28 days). A normal period lasts for 3–7 days. Menstrual blood loss of 30–50 ml/month is normal. Menstrual blood loss is considered as excessive when it is greater than 80 ml/month. It is, however, rarely measured in clinical trials, and heavy menstrual loss should be defined clinically.

Physiological amenorrhoea

Uterine and lower genital tract disorders

Ovarian disorders

Ovarian disorders

Premature ovarian failure

In this condition, ovarian follicles are depleted from the ovary before the normal age of the menopause, and a premature menopause ensues. In addition to amenorrhoea, the patient may complain of menopausal symptoms such as hot flushes, loss of libido, etc. This condition is not uncommon: 1% of women will have ovarian failure by the age of 40. Premature ovarian failure is found in around 10% of women with amenorrhoea.

Polycystic ovarian syndrome

Polycystic ovarian syndrome (PCOS) is a functional derangement of the hypothalamo–pituitary ovarian axis associated with anovulation. The pathophysiology of PCOS remains poorly understood. Insulin resistance is a feature, and a genetic element to the disorder has been proposed. Women with PCOS are more at risk of developing Type II diabetes.

In women with PCOS, LH levels are relatively high and FSH levels are relatively low, leading to an elevated LH:FSH ratio. Oestradiol levels tend to be within the normal range. Production of androgens is stimulated by the elevated levels of LH; increased levels of testosterone, androstendione and DHA are secreted by the ovary. Some of these androgens are converted to oestrogen in peripheral tissues. In response to high androgen levels, sex hormone binding globulin (SHBG) is reduced by about 50%, leading to an increase in the proportion of unbound, active, androgens. Hence, androgenic side effects are common, despite only a modest rise or even normal levels of total serum testosterone levels.

Pituitary disorders

Pituitary tumours are normally benign. However, as they grow in a confined space, they may cause symptoms by compressing surrounding tissue and structures. Functioning pituitary tumours may exert effects because of the hormones they release. The commonest of these are prolactin secreting pituitary tumours, accounting for 50% of all pituitary adenomas.

Hyperprolactinaemia

Prolactin is secreted from the anterior pituitary, and the normal blood level is between 150 and 600 mU/L depending on the laboratory. During pregnancy, there is a 10-fold increase in serum prolactin levels. Non-physiological hyperprolactinaemia, which occurs when the woman is non-pregnant, can cause amenorrhoea or galactorrhoea (inappropriate lactation) or both. Hyperprolactinaemia is the principal cause of amenorrhoea in around 20% of women with this condition.