The early stages
Noticeable diffuse thinning in women usually starts after menopause when the production of the female hormone estrogen slows down dramatically or stops altogether. Before menopause when production of estrogen is high, this hormone has a protective effect against the small amount of testosterone that women also produce.
As I wrote in regard to male pattern baldness, the enzyme 5-alpha reductase in scalp tissue converts circulating (free) testosterone into DHT. The hormone DHT (dihydrotestosterone) can harm hair follicles by making them shrink or causing them to enter prematurely into the resting stage of the hair cycle. Before menopause the estrogen in a woman's body counteracts the small amount of testosterone she produces in the adrenal cortex and makes it less available to conversion into DHT.
What it looks like
When DHT does its work in men, the result is usually the characteristic U-shaped pattern of hair loss. Women very rarely have this kind of hair loss. The hair loss in women is more diffuse and there are seldom bald spots. The frontal hairline is also spared in most cases. But still the result can look terrible to a woman who has had luxuriant hair just a few years before. About fifteen percent of women are afflicted with a degree of hair loss that is depressingly evident. This hair loss happens at a slower rate than in men and it happens at a much later time in life. But the wisdom of age does not make noticeable hair loss in a post-menopausal woman less traumatic.
The type of hair loss known as TE is more common in women than in men. It is characterized by many hairs entering the telogen or resting stage of the hair cycle at one time. The profuse shedding that occurs during TE can seem overwhelming to women experiencing it. The condition is often brought on by crash dieting (losing more than two pounds a week), prolonged emotional or physical stress, post-pregnancy hormone changes, and severe illness. When these triggering factors are removed, TE hair loss usually ceases. The recovery of the lost hair, however, may take six months to a year. Recovery of this kind of hair loss is probable even without treatment.
To speed up recovery from TE many professionals recommend bringing serum ferritin levels up between 40 and 60 ng/ml (nanograms per milliliter). The wide normal range for this level of iron stores in the body is between 12 to 150 ng/ml for women, but the lower end of this range is not sufficient to speed up hair growth. Eating iron-rich foods (lean meat) will usually raise the level over a period of time. Vegetarians may have a hard time bringing serum ferritin to the levels needed though.
Rogaine used for only a few months sometimes will start the recovery process for TE. With TE the Rogaine will not have to be used after the hair begins to grow back.
I know many women, mostly ballroom dancers, who are proud of the way they look and who are acutely aware of the way others look at them when they are not wearing a wig. My inclination here is to inject some gentle humor to lighten this up a bit, but my experience with the pain some of these women have because of hair loss cancels out any thought of humor. The agony of women suffering from hair loss is I think deeper than that of men with the same problem. This is because much of a woman's self-image depends on the way she looks in the mirror.
Continue to - Types of Treatment
Androgens in women
Most of the women with AGA (androgenic alopecia) do not have higher levels of androgens than women without AGA. The thinning of the hair can happen because of a high number of receptor cells and an extra sensitivity of these cells to the androgens.