Women develop excessive body or facial hair due to higher-than-normal levels of male hormones. Male hormones are called androgens, and they include testosterone. All females produce androgens, but the levels normally remain low. Certain medical conditions can cause a woman to produce too many androgens, causing male-pattern hair growth and other unwanted male characteristics, such as a deep voice.

Polycystic ovarian syndrome (PCOS) is one common cause of hirsutism. Benign cysts that form on the ovaries can affect hormone production, leading to irregular menstrual cycles and decreased fertility. The Office of Women’s Health (OWH) states that women with PCOS often have moderate-to-severe acne and tend to be overweight.

Other forms of hormonal imbalance that cause excessive hair growth include the following adrenal gland disorders:

  •     adrenal cancer
  •     adrenal tumors
  •     congenital adrenal hyperplasia
  •     Cushing disease

The adrenal glands are located just above your kidneys and are responsible for hormone production. People with congenital adrenal hyperplasia are born without an enzyme that’s necessary for hormone production. Those with Cushing disease have higher-than-normal levels of cortisol. Cortisol is sometimes called the “stress hormone.” All of these conditions can affect the way your body produces androgens.

Hirsutism tends to run in families. You may be more likely to have unwanted hair growth if your mother, sister, or another female relative also has it.

Hirsutism, also called hypertrichosis, is the growth of terminal hair or thickened vellus hair in places more typical for men than women. It can either be genetic or caused by one of the body’s natural reactions to hormonal and biochemical imbalances, like insulin resistance and high levels of androgen hormones.

How severely or quickly hirsutism develops, and where it occurs, varies. The three main factors include:

  •     Production of abnormally high levels of androgens like testosterone.
  •     The amount of androgens being bound up by SHBG, or sex-hormone–binding globulin, versus how much is freely available in the bloodstream.
  •     The degree that androgen receptors around the hair follicles themselves become sensitized to androgen hormones.

Androgens are produced by your ovaries, your adrenal glands, and also peripherally in your fat tissues. From there, they are transported throughout the bloodstream to your hair follicles, where testosterone is converted into its more potent, follicle-active form. More “sensitive” hair follicles can spend a longer time in the anagen, or active, phase of hair growth.

If you have higher-than-usual levels of free testosterone, or your hair follicle receptors have become hypersensitive to androgens, excess or unusual hair can grow anywhere on your body — even on the palms and soles of the feet. Increased facial hair, for example, commonly develops in menopausal women, and is sometimes said to be caused by “unopposed androgen.” But for most women, hirsutism is typically identified in the moustache, beard, chest (usually between the breasts or around the nipples), and genital regions.