Introduction to hirsutism and virilism

Both hirsutism and virilism are caused by either increase in plasma free androgen concentrations or increased tissue sensitivity to androgens.

Basically this increase/sensitivity may lead to hirsutism (excessive hair growth) or virilism (marked masculinization).

The most important androgen is testosterone and over 50% is produced by the ovaries in women (direct secretion) and by peripheral conversion of androstenedione. The remainder of the androgens is produced by the peripheral conversion of adrenal androgens,androstenedione and dehydroepiandrosterone (DHA).

It is very difficult to trace the source of a slightly raised plasma androgen level because of extensive interconversions. It must be noted that generally an increase in plasma testosterone is of ovarian origin and raised conentrations of DHA or DHAS is of adrenocortical origin.

The plasma free hormone is responsible for the biological activity of the testosterone. The sex hormone binding globulin influences the biological activity of the hormone.

Sex hormone binding globulin is increased bu oestrogens and in hyperthyroidism. It is decreased by androgens,hypothyroidism and obesity.

Hirsutism

Is excessive growth of hair in a male distribution. Hirsutism is more common than virilism. It is more common in some tribes and in some families.Therefore investigations should not be started until familial or racial/tribal origin is not excluded.In hirsutism the plasma testosterone is usually only slightly raised (upper limit of the normal range).

Causes of hirsutism:

i)Polycystic ovary syndrome (Polycystic ovary disease-PCOS,PCOD). This is the commonest cause of hirsutism. Patients also usually present with obesity, infertility and menstrual disturbances. In PCOD plasma testosterone concentrations are usually at the upper end of the female reference range. In obese individuals plasma concentrations of SHBG are reduced, this leads to an increase in the plasma concentration of free testosterone.The plasma prolactin concentration is increased and multiple subcapsular ovarian cysts are found on ultrasound scan.

ii) Late onset congenital adrenal hyperplasia (CAH). This is most frequently caused by 21 alpha hydroxylase deficiency.Some individuals with CAH may have amenorrhoea. The confirmation of the diagnosis is by demonstrating raised plasma 17 alpha hydroxyprogesterone and testosterone. 17 alpha hydroxyprogesterone may either be elevated under basal conditions or after stimulation with ACTH.

Virilism

In virilism patients have excessive hair growth and additional evidence of excessive androgen secretion such as an enlarged clitoris (clitoromegaly).There is also receding temporal hair, deepening of the voice and breast atrophy.

Virilism is rare but it is a much more serious condition than hirsutism.

There is always increased plasma androgen concentration in virilism.

Causes of virilism:

i)Ovarian tumours such as arrhenoblastomas and hiatus-cell tumours). These secrete androgens ,mainly testosterone.

ii)Adrenocortical disorders:

-Tumours eg carcinomas

-Hyperplasia: This includes pituitary-dependent Cushing’s disease (rarely) ;and congenital adrenal hyperplasia.

-There is an increase in plasma DHA and DHAS.

References:

Pages 140 to 141. The reproductive system. Clinical Chemistry in Diagnosis and Treatment by Philip D. Mayne.Sixth edition.

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