Hirsutism in Women: Causes, Symptoms & Hormones

The hormonal causes of hirsutism

In most cases, hirsutism is caused by an excess of androgens, known as hyperandrogenism, or by an increased effect of these hormones on the hair follicles. To understand the causes, it is worth looking at the hormones involved.

The role of androgens and testosterone

Androgens are male sex hormones, primarily testosterone and its derivatives. Women naturally produce small amounts in the ovaries and adrenal glands. Testosterone circulates in the blood partly freely and partly bound, and can be converted into dihydrotestosterone (DHT) in target tissues, an androgen that acts even more potently on androgen receptors. Hair follicles in certain regions react sensitively to it: It is only through these hormones that fine vellus hairs develop into coarse terminal hairs during puberty. With excessive androgen influence, hair growth in male patterns intensifies.

Important to know:Laboratory values correlate poorly with the extent of hirsutism.Many women with hirsutism have elevated testosterone levels. However, there are also women with normal androgen levels who are significantly affected, and conversely, women with high testosterone and few external signs. The reason lies in the different sensitivity of the hair follicles. Genetic factors influence how strongly the hair follicle reacts to a given amount of androgen. Increased local activity of 5-alpha reductase or more androgen receptors in the skin can lead to strong hair growth, even if blood levels are barely elevated. This case is called idiopathic hirsutism and accounts for about 10 percent of cases.

SHBG and insulin: why insulin resistance increases hair growth

Another important factor is sex hormone-binding globulin (SHBG). SHBG binds androgens in the blood, thereby regulating the amount of free testosterone available. Only free testosterone can enter cells and act. Insulin plays an indirect but crucial role here: high insulin levels, as are common in insulin resistance, lower SHBG production in the liver. Less SHBG means more free testosterone. Women with insulin resistance, as is typical in PCOS, therefore often have low SHBG levels and elevated free testosterone. Insulin can also stimulate androgen production in the ovaries, thus completing the cycle. Conversely, insulin-lowering measures often lead to an increase in SHBG and a reduction in hirsutism, although usually not sufficient as a sole therapy.

PCOS as the most common cause

By far the most common cause of hirsutism is Polycystic Ovary Syndrome (PCOS). This is an endocrine disorder characterized by chronic hyperandrogenism and ovulatory dysfunction. According to the Rotterdam criteria, at least two of the following three features are typically present:

1. clinical or biochemical signs of hyperandrogenism, such as hirsutism, acne, or elevated testosterone
2. infrequent or absent ovulations
3. a polycystic ovary appearance on ultrasound

More than 80 percent of women with hirsutism have PCOS. Conversely, approximately 65 to 75 percent of PCOS patients show hirsutism as a visible sign of androgen excess. PCOS is common overall and affects a significant proportion of women of childbearing age, depending on the criteria and population. Nevertheless, not every woman with hirsutism automatically has PCOS. Excluding other causes is important.

Further possible causes

• Idiopathic hirsutism:around 10 percent of cases. Normal hormone levels and regular cycle, but genetically determined high sensitivity of hair follicles. PCOS and idiopathic hirsutism together account for about 90 to 95 percent of all cases.
• Non-classic congenital adrenal hyperplasia (CAH):a milder form of congenital adrenal hyperplasia, often due to 21-hydroxylase deficiency. Can cause hirsutism, acne, and menstrual irregularities.
• Androgen-secreting tumors:very rare, but important to rule out. Lead to rapidly progressing hirsutism with virilization. Testosterone levels above approximately 150 ng/dL are considered a warning sign.
• Cushing's syndrome:an excess of cortisol can promote hirsutism, usually associated with truncal obesity, high blood pressure, and insulin resistance.
• Medications:anabolic steroids, danazol, certain progestins with androgenic partial effects, or valproate have been linked to hirsutism. Minoxidil and phenytoin are more likely to cause hypertrichosis.
• Genetic and ethnic factors:the expression of body hair is strongly genetically influenced. Women of Mediterranean, Middle Eastern, or South Asian descent naturally have stronger hair growth. The transitions to idiopathic hirsutism are fluid.

These causes can also occur in combination, such as stronger familial hair growth with mild PCOS simultaneously. A careful medical evaluation is therefore important.

When you should have hirsutism checked

As a general rule: Any clinically relevant hirsutism should be medically examined at least once. In these situations, an evaluation is particularly important:

• Rapid onset or rapid increase:if severe hair growth develops within months, especially with signs of virilization such as a deepened voice. In this case, hormonal diagnostics should be carried out promptly.
• Pronounced hirsutism before the age of 25:may indicate non-classic CAH. A determination of 17-hydroxyprogesterone is then useful.
• Hirsutism with menstrual cycle disorders:this constellation suggests PCOS. Since PCOS also carries long-term metabolic risks, the diagnosis should be made.
• Severe emotional distress:regardless of laboratory values. If hair growth bothers you, that is reason enough for an evaluation.

An evaluation usually includes anamnesis, physical examination, and laboratory tests. Relevant blood values are total testosterone and calculated free testosterone via SHBG, DHEA-sulfate, androstenedione, possibly 17-hydroxyprogesterone, as well as orientationally LH and FSH. Professional societies recommend determining testosterone in cases of abnormal hirsutism scores, but to forgo hormone determination in cases of normal cycles and normal scores.

Conclusion

Hirsutism is not a minor cosmetic issue, but in most cases, it is the most visible sign of a hormonal imbalance. More than 80 percent of affected women have PCOS. At the same time, it is true that your blood values alone do not tell the whole story, because how strongly your hair follicles react to androgens is individual and genetically determined.

This means two things. Firstly: If your values are normal, but you are still affected, you are not imagining it. Secondly: Because insulin resistance plays a direct role via the SHBG mechanism, blood sugar metabolism is one of the levers where something can actually be changed. However, the first step is always to have the cause properly assessed.