In MPB, follicles slowly become miniaturized and the anagen phase of the hairs is reduced. Due to the shortened growing phase, the hair’s maximum length is reduced. At the same time, the telogen phase lengthens. This cycle slowly becomes more and more weighted toward the telogen phase.

Over time, the anagen phase becomes so short that the new hairs do not even peek through the surface of the skin.Over time, the anagen phase becomes so short that the new hairs do not even peek through the surface of the skin.

Added to this, telogen hair growth is less well anchored to the scalp, explaining why there is often hair loss noted during showering. Miniaturization of the follicles causes the shaft of the hair to become thinner and thinner with each cycle of growth. Eventually, normal (terminal) hairs are reduced to villus hairs. Villus hairs are the soft, light hairs that cover a baby and mostly disappear during puberty in response to androgens.

Hair follicles are very sensitivity to Dihydrotestosterone (DHT).  DHT is a sex steroid, meaning it is produced in the gonads. DHT is also an androgen hormone, from the Greek prefix “andro” meaning “masculine.”

Androgens are responsible for the biological characteristics that typify males – deep voices, hairy chests and increased muscle mass, for example.

Testosterone is converted to DHT by specific enzymes. Roughly 5% of free testosterone is normally converted into DHT. DHT is a particularly potent androgen, five times more potent than testosterone. It attaches to the same sites as testosterone but with more ease and remains bound for longer periods of time.

Male pattern baldness is generally characterized with the onset of a receding hairline and thinning crown. Hair in these areas including the temples and mid-anterior scalp appear to be the most sensitive to DHT. This pattern eventually progresses into more apparent baldness throughout the entire top of the scalp, leaving only a rim or “horseshoe” pattern of hair remaining in the more advanced stages of MPB.For some men even this remaining rim of hair can be affected by DHT.

Androgenic Alopecia in women

Is a multi-factorial condition in which genetic predisposition + circulating androgens viz testosterone androsteinedione, and dihydrotestosterone (DHT) are key factors in a process of progressive hair follicle miniaturisation and reduction in the anagen (hair growing) phase. Follicles effectively ‘shrink’ to produce vellus hairs. Caucasoids have a higher susceptibility than Afroid’s or Mongoloids. This condition may warrant endocrinological investigation.

How the condition differs from that in men:

  1. The progression is slower – possibly due to a level of ‘follicular protection’ afforded by estrogen.
  2. Hair loss is diffuse and does not conform to the traditional patterns of loss in males.
  3. Hair loss may worsen following menopause with the development of baldness especially at the vertices.
  4. In men the condition is due to genetic predisposition and is usually age related.
  5. In women the condition can present at any time associated with underlying medical conditions. viz: polycystic ovarian syndrome, thyroid disorders,  anemia, chronic illness, use of certain medications.

Expert opinion currently doubts that the condition in women is the same as that in men. Correct diagnosis is essential, and may require blood tests, or scalp biopsy.

Conclusion: The most common cause of Male Hair Loss and Female Hair Loss is inheritance from either or both parents. Certain hair follicles contain receptors sensitive to the hormone ‘Dihydrotestosterone’ (DHT). This hormone is a by-product of testosterone which surges at puberty. Fortunately, in the vast majority of cases those follicles at the back and sides of the head do not contain the receptor sensitive to DHT and therefore last a lifetime even when transplanted to a different area.
A man may expect to lose hair as he gets older, especially if his father, uncles, or other near relatives had male-pattern baldness. A woman does not generally expect to lose hair even if there is a history of hair loss in male or female relatives. There has been a general belief that thinning hair and baldness is a ‘male thing’.

The fact is, many women do experience hair loss at young to middle age and the incidence of the most common type of female hair loss (female androgenetic alopecia) seems to be increasing. Other causes of female hair loss include , low iron levels, hormonal imbalance etc.


Dihydrotestosterone (DHT) is a derivative or by-product of testosterone. Testosterone converts to DHT with the aid of the enzyme Type II 5-alpha-reductace, which is held in the hair follicle’s oil glands. While the entire genetic process of male pattern baldness is not completely understood, scientists do know that DHT shrinks hair follicles, and that when DHT is suppressed, hair follicles continue to thrive. Hair follicles that are sensitive to DHT must be exposed to the hormone for a prolonged period of time in order for the affected follicle to complete the miniaturization process. Today, with proper intervention this process can be slowed but never can be stopped, the only solution is hair transplantation.


The Hamilton-Norwood scale is a way of measuring male pattern baldness. It was introduced by Dr. James Hamilton in the 1950s and later revised and updated by Dr. O’Tar Norwood in the 1970s.

There are 2 main types of balding, anterior (front) and vertex (back), as this alternate view of the Norwood scale shows a bit more clearly.

This chart of hair loss pictures is a useful tool for diagnosis (and to avoid misdiagnosis) and for describing the extent of hair loss for treatment  purposes.


Norwood 1

Normal head of hair with no visible hair loss.

Norwood 2

The hair is receding in a wedge-shaped pattern.

Norwood 3

Same receding pattern as Norwood 2, except the hairline has receded deeper into the frontal area and the temporal area.

Norwood 4

Hairline has receded more dramatically in the frontal region and temporal area than Norwood 3 and there is the beginnings of a bald spot at the back of the head.

Norwood 5

Same pattern as Norwood 4 but much reduced hair density.

Norwood 6

The strip of hair connecting the two sides of the head that existed in Norwood 4 and 5 no longer exists in Norwood 6.

Norwood 7

Norwood 7 shows hair receding all the way back to the base of the head and the sides just above the ears.