Hypertrichosis is defined as excessive hair growth beyond what is considered normal for a person’s age, sex, and ethnicity. It is a symptom rather than a single disease, affecting any part of the body. While the hair growth stems from hair follicles, the underlying causes often involve a complex interplay of the body’s regulatory systems. Many cases of acquired excessive hair growth are linked to hormonal imbalances, though non-endocrine factors also play a significant role.
Hypertrichosis Versus Hirsutism: Clarifying the Conditions
It is important to distinguish hypertrichosis from hirsutism, as the public often confuses the two. Hypertrichosis is a broad term for excessive hair growth that can be generalized, covering the entire body, or localized to a specific area. This excess growth can involve fine vellus hair, coarse terminal hair, or downy lanugo hair. Hypertrichosis affects both men and women and is not necessarily dependent on male hormones.
Hirsutism, by contrast, occurs exclusively in women and children. This condition is characterized by the growth of coarse, dark, terminal hair in a male-like pattern, such as on the upper lip, chin, chest, back, and lower abdomen. Hirsutism is almost always related to an excess of androgens, the male sex hormones, or an increased sensitivity of the hair follicles to these hormones. Because of this direct hormonal link, hirsutism is the condition most commonly associated with glandular dysfunction.
The crucial difference lies in the location and hormonal dependency of the hair growth. Hypertrichosis can occur anywhere on the body and may be caused by factors unrelated to hormones. Hirsutism is strictly defined by hair growth in androgen-dependent areas and serves as a strong indicator of an underlying endocrine issue.
Endocrine Glands and Hormonal Drivers of Excessive Hair Growth
The glands most frequently implicated in hormonally driven excessive hair growth, particularly hirsutism, are the ovaries and the adrenal glands. These organs are the primary producers of androgens, the hormones that stimulate the conversion of fine vellus hair into coarse terminal hair. When these glands malfunction, they can overproduce androgens, leading to symptoms of hair excess.
Ovaries
The ovaries are a common source of hormone imbalance. Polycystic Ovary Syndrome (PCOS) is the most frequent cause of hirsutism, accounting for over 70% of cases. PCOS is a complex endocrine disorder where the ovaries often produce excess testosterone and other androgens. This leads to male-pattern hair growth, irregular menstruation, and sometimes acne. Ovarian tumors, though rare, can also rapidly cause hirsutism by secreting high levels of androgens.
Adrenal Glands
The adrenal glands, located atop the kidneys, are another significant player in the endocrine regulation of hair growth. Conditions like Cushing’s Syndrome, which results in the overproduction of the hormone cortisol, can cause the adrenal glands to also secrete high levels of adrenal androgens. Congenital Adrenal Hyperplasia (CAH), a genetic disorder, causes the adrenal glands to produce irregular amounts of steroid hormones, often resulting in an excess of androgens and subsequent hirsutism.
Pituitary Gland
The pituitary gland, located at the base of the brain, also plays an indirect but significant role through its control of the adrenal and ovarian systems. The pituitary releases adrenocorticotropic hormone (ACTH), which stimulates the adrenal glands, and gonadotropins, which regulate the ovaries. A pituitary tumor, for example, can cause Cushing’s disease by over-secreting ACTH. This then drives the adrenal glands to produce excessive androgen, ultimately leading to hair growth.
Systemic Conditions and Non-Glandular Factors
Many cases of hypertrichosis are not related to endocrine gland dysfunction and must be considered separately. Acquired hypertrichosis, which develops later in life, is often a side effect of certain medications. Drugs such as cyclosporine, used to suppress the immune system, and minoxidil, a common hair growth stimulant, can cause generalized hair growth that is not dependent on androgens.
Underlying systemic illnesses can also trigger excessive hair growth through non-hormonal pathways. Severe malnutrition, such as that seen in anorexia nervosa, can lead to the growth of fine lanugo hair over the body as a protective mechanism against heat loss. Metabolic disorders like Porphyria Cutanea Tarda, a disorder affecting the skin and liver, are also known to be associated with generalized hypertrichosis.
Furthermore, the sudden, rapid onset of fine hair growth, known as acquired hypertrichosis lanuginosa, can be a sign of internal malignancy, often preceding the diagnosis of cancer. Finally, congenital forms of hypertrichosis are present at birth and are purely genetic, resulting from mutations that affect the hair cycle, rather than any hormonal imbalance from the endocrine system. These factors demonstrate that while glands are the source of hormonal drivers for hair growth, they are not the sole cause of hypertrichosis.