Hair growth and distribution may vary among different ethnic groups but thick female facial hair, the presence of a visible mustache or beard in women, are considered to be uncharacteristic of the female gender. Hair growth is primarily dependent on the sex hormones, androgens and estrogen. Androgens, like testosterone are usually responsible for thicker hair while the female sex hormones like estrogen are responsible for fine hair.
The presence and distribution of body hair is usually noted at puberty and continues to grow till early adulthood. This type of hair, after the onset of puberty, is known as terminal hair compared to the fine downy hair (vellus hair) present in early childhood. Hirsutism should be differentiated from hypertrichosis which is excessive hair growth throughout the body (generalized) or isolated to specific areas (localized). Hirsutism refers to androgenic hair growth patterns and can affect both men and women. Usually hirsutism is not noticed or considered a problem in men since it corresponds to normal body hair growth patterns associated with adult males.