In response to the question in last Monday’s lecture, I found the following information on female baldness from the following sites:
http://ezinearticles.com/?Female-Baldness&id=126811
http://www.forhair.com/women_female_hair_loss.htm
http://en.wikipedia.org/wiki/Alopecia_areata
EXPLANATION I – THE MORE COMMON FORMS OF BALDNESS.
The explanation requires some background on the genetics of male pattern balness. The genetic reason for Pattern Baldness is linked to your mother’s X-Chromosome. Everyone get one-half of their genetic make-up from their mother and their father. The final chromosome pair of the 23 pairs is the sex determining set. While males are XY and females are XX the determination of an individuals sex is made by the father. It is the father who gives either the X chromosome, which matches with the woman’s X resulting in XX and a female child or the Y chromosome which joins with the woman’s X resulting in an XY match and a male child. It is the X chromosome or female sex chromosome that contains the gene for Male Pattern Baldness.
Since men have only one X chromosome, the gene for baldness is a single expression gene that shows up because there is no possible dominant gene to suppress what would normally be a recessive or hidden characteristic. Since Male Pattern Baldness gene is only on the X chromosome and men can only get that chromosome from their mothers, it is simple to see how this type of baldness is passed from mother to son.The fact that it seems that men in families often have many generations of bald men tend to make this explanation of hard to believe, yet genetics explain it. Male Pattern Baldness is a condition that as previously stated is on a gene on the X chromosome. Since this form of baldness is recessive, it will be hidden if only
one of the dominant genes is present. Since women have the XX chromosome pair, baldness will not occur unless both chromosomes have the recessive gene that causes baldness. A woman could have one of three genetic conditions:
Both X chromosomes with normal gene represented by Xn Xn this would appear as normal. One normal and one baldness gene on the X chromosome pair represented by Xn Xb, this would appear as normal. Both X chromosomes with the baldness gene represented by Xb Xb, this would appear as a woman with pattern baldness
Given these three female genetic possibilities there are 4 possibilities for male offspring:
1 for the first woman – 1 normal male XnY
2 for the second woman – 1 normal/ 1 bald male XnY / XbY
1 for the third woman – 1 bald male XbY
Once a male is born with the baldness gene he automatically passes it on to all his female offspring. If his mate is normal with the gene for baldness (Xn Xb) each female child born has a 50-50 chance of being born with male pattern baldness.
Women can be affected if they receive the recessive X for balding from both parents, although the extend to which balding is common is not usually to the same extent as that seen in men.
Explanation II – Alopecia
The precise etiology (cause of disease) is unknown. However, research has indicated it occurs more frequently in people who have affected family members, suggesting that heredity may be a factor. In addition, it is slightly more likely to occur in people who have relatives with autoimmune diseases. The condition is thought to be an autoimmune disorder in which the body attacks its own hair follicles and suppresses or stops hair growth. There is evidence that T cell lymphocytes cluster around these follicles, causing inflammation and subsequent hair loss. An unknown environmental trigger such as emotional stress or a pathogen is thought to combine with hereditary factors to cause the condition.
Explanation III – Other balding factors
Most instances of baldness in females are diagnosed as the result of a deficiency in endocrine hormones. This is why women may find a gradual or dramatic thinning of hair at or after the onset of menopause. Genetic predisposition (androgenetic alopecia) is the cause of almost 90% of female baldness. The use of oral contraceptives is also a known cause for it since birth control pills manipulate a woman’s hormonal balance.
Other reasons are the natural aging process, the use of unsuitable hair products, drastic hair styling habits, and grossly improper nutrition. Certain skin disorders like alopecia areata can also cause hair loss in females, which usually occurs in small patches rather than progressively expanding areas.
In quite rare instances, trichotillomania is a factor – this is an obsessive-compulsive disorder that causes the willful uprooting of hair and is usually noted in pre-teenaged or teenaged females. Stress – the bane of modern civilization and often thought to be responsible for hair loss in both males and females – is definitely not a causative factor.
