The prevalence of hirsutism and what causes it

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Prevalence of Hirsutism

Hirsutism is a hair production disorder that approximately affects between 5% and 15% of women. At least 5% of women of reproductive age suffer from this ailment. Though these prevalence figures are not final, with experts often considering them to be an underestimation, they are generally accepted.

In US alone there are said to be at least 4 million hirsute premenopausal women, who collectively spend 1.5 billion dollars annually on hair removal products and processes. Hirsutism in women is defined as unwanted and excessive terminal hair growth in a male-like pattern in various androgen-sensitive body parts.

Methods to determine the prevalence of hirsutism

The measurement of the occurrence of hirsutism is dependent on the method of research and the population under survey. The clinical process of adjudging the prevalence of hirsutism is a subjective and observation-based evaluation of the extent of the patient’s hair disorder condition, coupled with associated medical tests. However, there are some scientific methods of measuring the prevalence of hirsutism. They are:

1. Ferriman-Gallway (F-G) score

This is the established and most prevalent system of measuring hirsutism. It was introduced in 1961 and initially it was based on the presence of hair production in 11 different areas namely the upper lip, chin, chest, upper back, lower back, upper abdomen, lower abdomen, arm, forearm, thigh, and lower leg. The survey was conducted at a medical clinic in UK and the cases were 430 successive females stated to be primarily of white ethnicity and aged 15 to 74 years.

The scorecard of every body part analyzed began from 0 (zero terminal hairs) to 4 (massive terminal hair growth or frankly hirsute). The survey also suggested that hair production over the forearm and lower leg were less androgen receptive. This was an important finding since androgen is the main hormone that determines terminal hair production and its dysfunction is one of the main causes of hirsutism. Excluding the other nine body parts, 4.3% of patients evaluated registered a count of greater than 7. Hence, the experts conducting the study concluded that a score of 8 or more suggests hirsutism. Later there have been various modifications of the method. Some have been based on the analysis of hair production preferentially in the sideburn region, lower jaw, and upper neck, or perineal region and this has led to new measurement processes.

2. Hatch and colleagues’ method

This is also a variation of the Ferriman-Gallwey technique. Hatch and his fellow experts maintained the conventional score card of 0 to 4 but referred to only nine of the body locations assessed by Ferriman and Gallwey. The lower legs and lower arms were not included in their research.

Based on this pattern many surveyors have conducted their own survey. One such survey prospectively reviewed 369 consecutive pre-menopausal women. Out of these 7.6%, 4.6%, and 1.9% registered a Ferriman and Gallwey count of 6 or more, 8, and 10, respectively and irrespective of their ethnicity (black or white). Hence, this led to a variant of the Ferriman and Gallwey count of 6 or more to mark the prevalence of hirsutism.

This study also agreed with the general estimate that hirsutism afflicts approximately 8% of women. It also suggested that among an estimate of 52 million women aged 15 - 44 years (US Census Bureau, July 2000 approximation) in the US, over 4.0 million pre-menopausal cases are hirsute. Out of this androgen-excess triggered hirsutism was recorded in majority.

3. Lorenzo’s study of hirsutism

This study was conducted on 300 random women (irrespective of racial differences) from a public health survey in Michigan. It score pattern was based on only five body regions namely chin, upper lip, chest, abdomen, and thighs and the count was the conventional 0 to 4. This survey did not record a hirsutism tally over 5 among any of the cases studied. Hence, from this analysis some experts concluded that the general score varies with the area of survey.

Apart from these three hirsutism measuring methods, there have also been studies that quantify the causes behind the syndrome. They are also indispensable for a proper prevalence study of hirsutism. Below is a common approximation (though there are many variations as well) of the prevalence of various factors that lead to hirsutism:

  • Polycystic Ovarian Syndrome (PCOS) - 70–80%
  • Hyperandrogenism - 6.8%
  • Hypothyroidism - 0.7%
  • The hyperandrogenic insulin-resistant acanthosis nigricans syndrome (HAIR-AN) - 3 %
  • 21-hydroxylase non-classic I adrenal hyperplasia (late-onset CAH) - 1.6%
  • 21 -hydroxylase-deficient congenital adrenal hyperplasia - 0.7%
  • Hyperprolactinemia - 0.3%
  • Androgenic tumors - 0.2%
  • Cushing’s syndrome - 0-1%
  • Idiopathic hirsutism - 4.7%

There are a few other non-androgenic causes of hirsutism as well, but their prevalence is very rare.


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