Types of Hair Grown
After shedding lanugo scalp hair as infants, humans normally grow two types of scalp hair, with most of it being terminal type hair.(6, 14)
The two types of hair differ in various ways:(6, 14)
- Diameter and length
- Color
- Hair shaft structure
- Root depth
- Location
The type of hair grown is determined by:
- Gender
- Location on the body, face, or scalp
- Hormonal influences
The adrenal glands start to produce large amounts of androgen hormones at around age eight. Once puberty begins hormone-sensitive vellus hairs growing on the body transform into terminal hairs. This occurs in areas such as the pubic regions in both genders; other areas in men include face, chest, and abdomen.(6, 15)
Patterned Hair Loss and Types of Hairs
Male common balding and female pattern hair loss can occur any time after puberty. Age of onset and extent of hair loss is influenced by:(15)
- Genetics in both men and women
- Hormones (such as testosterone, DHT, estrogen, insulin, and sex hormone binding globulin)
- Medical conditions (such as polycystic ovary syndrome and adrenal disorders)
In all cases of patterned hair loss, androgen-sensitive terminal hairs on the scalp gradually become miniaturized and resemble vellus hairs. When they fall out at the end of their growth cycle they are not replaced with terminal hairs.(15)
Eventually, this can lead to areas of complete balding following distinct patterns and/or diffuse thinning through the top of the head. Patterns and amount of hair loss is influenced by gender and slightly by ethnicity and/or race.(15)