Introduction
Background
Hirsutism is defined as the excessive growth of thick dark hair in locations where hair growth in women usually is minimal or absent. Such male-pattern growth of terminal body hair usually occurs in androgen-stimulated locations, such as the face, chest, and areolae.
Idiopathic hirsutism in an elderly woman.
Although the terms hirsutism and hypertrichosis often are used interchangeably, hypertrichosis actually refers to excess hair (terminal or vellus) in areas that are not predominantly androgen dependent. Whether a patient is hirsute often is difficult to judge because hair growth varies among individual women and across ethnic groups. What is considered hirsutism in one culture may be considered typical in another. For example, women from the Mediterranean and the Indian subcontinent have more facial and body hair than do women from East Asia, sub-Saharan Africa, and northern Europe. Dark-haired, darkly pigmented individuals of either sex tend to be more hirsute than blond or fair-skinned persons.
In most cases, hirsutism is a benign condition and is primarily of cosmetic concern. However, when hirsutism is accompanied by masculinizing signs or symptoms, particularly when these arise well after puberty, hirsutism may be a manifestation of a more serious underlying disorder such as an ovarian or adrenal neoplasm. Fortunately, these disorders are rare.
Pathophysiology
Hirsutism can be caused by abnormally high androgen levels or by hair follicles that are more sensitive to normal androgen levels. Therefore, increased hair growth often is observed in patients with endocrine disorders characterized by hyperandrogenism, which may be caused by abnormalities of the ovaries or the adrenal glands.
The physiologic mechanism proposed for androgenic activity consists of the following 3 stages:
- Production of androgens by the adrenals and ovaries
- Androgen transport in the blood on carrier proteins (principally sex-hormone–binding globulin [SHBG])
- Intracellular modification and binding to the androgen receptor
In short, central overproduction of androgen, increased peripheral conversion of androgen, decreased metabolism, and enhanced receptor binding are each potential causes of hirsutism. For circulating testosterone to exert its stimulatory effects on the hair follicle, it first must be converted into its more potent follicle-active metabolite, dihydrotestosterone. The enzyme, 5-alpha-reductase, which is found in the hair follicle, performs this conversion.
Overproduction of androgens results in an increased hair follicle size, hair fiber diameter, and duration of time hair follicles spend in the anagen (growth) phase. In addition to a change in hair quality and volume, oilier skin and hair may result from excess androgen secretion. The distribution of hair in women with high androgen levels is also altered. Excessive hair growth occurs in androgen-sensitive regions, but hair loss occurs on the scalp.1The severity of hirsutism does not correlate directly with the level of increased circulating androgens because of individual differences in conversion to 5-alpha-reductase and androgen sensitivity of hair follicles.
Testosterone stimulates hair growth, increasing the size and intensifying the pigmentation of hair. Estrogens act in opposition, slowing growth and producing finer, lighter hairs. Progesterone has minimal effect on hair growth.
The amount of free testosterone—the biologically active androgen that, after conversion to dihydrotestosterone, causes hair growth—is regulated by SHBG. Lower levels of SHBG increase the availability of free testosterone. SHBG levels decrease in response to the following:
- Exogenous androgens
- Certain disorders that affect androgen levels, such as polycystic ovarian syndrome (PCOS): See Media File 1.
The photograph depicts hirsutism in a young woman with polycystic ovarian syndrome. Note the acne lesions and excessive hair on her face and neck.
- Congenital or delayed-onset adrenal hyperplasia
The patient has late-onset congenital adrenal hyperplasia. She has clinical features similar to those found in polycystic ovarian syndrome, including hirsutism, acne, obesity, diabetes, and menstrual irregularities.
- Cushing syndrome
- Obesity
- Hyperinsulinemia
- Hyperprolactinemia
- Excess growth hormone
- Hypothyroidism
Conversely, SHBG levels increase with higher estrogen levels, such as the levels that occur during oral contraceptive therapy. The resultant increased SHBG levels lower the activity of circulating testosterone.
Frequency
United States
Hirsutism is common and is estimated to occur in 1 in 20 women of reproductive age.
International
Familial hirsutism is found most commonly in southern European and South Asian countries, in which it is considered to be a normal trait. Hirsutism indicative of underlying endocrinopathy varies from culture to culture, depending on the incidence of the various endocrinopathies in a particular society.
Mortality/Morbidity
Hirsutism is a symptom, rather than a disease. Primarily, hirsutism is of cosmetic and psychological concern; however, it may indicate the presence of more serious associations, such as adrenal hyperplasia and ovarian tumors, particularly if it develops well after puberty.
Race
Familial hirsutism is noted most frequently in dark-skinned white persons. It is uncommon in sub-Saharan and African American blacks and is observed least commonly in East Asians and Native Americans.
Age
The onset of hirsutism depends on its cause. Familial or ethnic hirsutism typically begins during puberty. Hirsutism resulting from congenital adrenal hyperplasia (CAH) begins early in childhood, while late-onset CAH and PCOS often have onset after puberty. The growth of facial hair commonly observed in postmenopausal women may be caused by unopposed androgen.
Clinical
History
In women, hirsutism exceeding culturally normal levels can be as distressing an emotional problem as the loss of scalp hair. The onset of hirsutism can take one of several forms. For example, in women with familial hirsutism, it often appears during puberty. Hirsutism usually develops gradually in patients with PCOS and CAH. Hirsutism appears abruptly when an androgen-secreting tumor arises.
Physical
A woman with hirsutism has excess terminal hair in a masculine pattern, but note that hirsutism may be difficult to evaluate in women who have blond hair.
A quantitative method of measuring hair growth, the Ferriman-Gallwey model, allows for the determination of the severity of hirsutism by assessing the extent of hair growth in 9 key anatomic sites, as follows:
- Face (particularly, moustache, beard, and temple areas; see Media File 2)
- Chest
- Areolae
- Linea alba
- Upper back
- Lower back
- Buttocks
- Inner thighs
- External genitalia
Other accompanying signs and symptoms may include some of the following:
- Acanthosis nigricans
- Obesity
- Pelvic mass
- Signs or symptoms of virility
- Signs or symptoms of Cushing syndrome
- Acne
- Alopecia
Causes
Ovarian causes of hirsutism
PCOS is a disorder that affects androgen levels. The most common cause of androgen excess and hirsutism is PCOS. Virilization is minimal, and hirsutism is often prominent. Characteristic features include menstrual irregularities, dysmenorrhea, occasional glucose intolerance and hyperinsulinemia, and, often, obesity. The hyperinsulinemia is believed to hyperstimulate the ovaries into producing excess androgens. Women with PCOS may show other cutaneous manifestations of androgen excess in addition to hirsutism, such as recalcitrant acne, acanthosis nigricans, and alopecia on the crown area of the scalp (a pattern that contrasts with the bitemporal and vertex androgenic alopecia seen in men). See Polycystic Ovarian Syndrome for more information.
Hirsutism may also be seen in women with the following ovarian conditions, most of which are associated with virilization:
- Luteoma of pregnancy
- Arrhenoblastomas
- Leydig cell tumors
- Hilar cell tumors
- Thecal cell tumors
Familial hirsutism
Familial hirsutism is not associated with androgen excess. Familial hirsutism is both typical and natural in certain populations, such as in some women of Mediterranean or Middle Eastern ancestry.
The photograph depicts familial hirsutism in a Pakistani woman.
Drug-induced hirsutism
Drugs that can induce hirsutism by their inherent androgenic effects include dehydroepiandrosterone sulfate (DHEA-S), testosterone, danazol, and anabolic steroids. Currently used low-dose oral contraceptives are less likely to cause hirsutism than were previous formulations.
Drugs such as phenytoin, minoxidil, diazoxide, cyclosporine, streptomycin, psoralen, penicillamine, high-dose corticosteroids, metyrapone, phenothiazines, acetazolamide, and hexachlorobenzene presumably exert their effects independently of androgens. The exact mode of action of these drugs on hair follicles is not known, but the same mechanisms do not appear to be involved in all patients.
Drug-induced hirsutism can be distinguished from drug-induced hypertrichosis, in which a uniform growth of fine hair appears over extensive areas of the trunk, hands, and face and is unrelated to androgen-dependent hair growth.
Adrenal causes of hirsutism
CAH in children (ie, the classic form of adrenal hyperplasia) may cause hirsutism. These children may be born with ambiguous genitalia, symptoms of salt wasting, and failure to thrive. Additionally, they may develop masculine features. See Congenital Adrenal Hyperplasia for more information.
Late-onset CAH usually occurs as an incomplete version of CAH and affects approximately 1-5% of women who are hyperandrogenic. In patients with late-onset CAH, hirsutism (without salt-wasting symptoms) may not develop until adulthood.
Signs of virilization and menstrual irregularities may not be observed until puberty or adulthood. Patients have clinical features that resemble PCOS.
Hirsutism and oligomenorrhea suggest 21-hydroxylase deficiency (elevated 17-alpha-hydroxyprogesterone). Another uncommon disorder is 3-beta-, 11-hydroxysteroid dehydrogenase deficiency (elevated 3-beta-, 11-hydroxysteroid levels), which may result in early- or late-onset CAH. See 3-Beta-Hydroxysteroid Dehydrogenase Deficiency for more information.
Cushing syndrome is a noncongenital form of adrenal hyperplasia characterized by an excess of adrenal cortisol production. The excessive growth is predominantly vellus (non–androgen dependent) hair.
Other causes
Less common but potentially serious disorders that may be associated with hirsutism include anorexia nervosa, acromegaly, hypothyroidism, hyperprolactinemia, and porphyria.
Idiopathic hirsutism or end-organ hirsutism occurs in a small proportion of women with hirsutism. Neither a familial form nor any detectable hormonal abnormality usually is diagnosed. Such patients have normal menses, normal-sized ovaries, no evidence of adrenal or ovarian tumors or dysfunction, and no significant elevations of plasma testosterone or androstenedione. Antiandrogen therapy may improve hirsutism in some idiopathic cases, which suggests that this form may be androgen induced. One theory is that many of these women may have mild or early PCOS and androgen levels in the upper-normal ranges. Eventually, idiopathic hirsutism probably may be recognized as a more subtle form of hypersecretion of hormones from the ovary or, possibly, the adrenal gland. A 2009 study found significant insulin resistance in nonobese patients with idiopathic hirsutism.2
More on Hirsutism |
 Overview: Hirsutism |
| Differential Diagnoses & Workup: Hirsutism |
| Treatment & Medication: Hirsutism |
| Follow-up: Hirsutism |
| Multimedia: Hirsutism |
| References |
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Further Reading
Keywords
hirsutism, hypertrichosis, hirsuties, excessive body hair, male-pattern hair growth
