Posts Tagged: Terminal Hair

Does Propecia Hair Loss Medication Effect Beard Growth?

July 6th, 2007

Q: I am a 21 yrs old male having serious hair loss over the last few years. I also have very little facial hair. Since Propecia is a DHT blocker can it inhibit beard growth?

A: As you suggest, it would be reasonable to assume that since DHT stimulates beard growth, blocking DHT (with finasteride) would tend to inhibit its growth. In practice, this does not seem to be the case, i.e. we don’t find that Propecia has any affect on facial hair. The reason is not clear.

It is interesting to note that testosterone stimulates growth of axillary and pubic hair, but not scalp hair. Scalp hair growth is not androgen dependent, only scalp hair loss is.

DHT stimulates terminal hair growth of the beard, trunk and limbs, external ears and nostrils. Of course, it also is responsible for the bitemporal reshaping of hairline as one passes into adulthood and causes male patterned baldness (androgenetic alopecia).

Topic: Drugs & Medications

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Posted by Robert M. Bernstein M.D. at 12:48 pm

Hair Loss Causes: What is Miniaturization and What is Effect of DHT on Hairs?

May 8th, 2007

Q: I have read that in the evaluation of a patient for hair restoration surgery some doctors use a densitometer to measure miniaturization – the decrease in size of hair diameters. I read that miniaturization is a sign of genetic hair loss, but when there is miniaturization of greater than 20% in the donor area, a person may not be a good candidate for hair transplants. Is this correct and does 20% miniaturization mean that 20% of the population of terminal hairs have become fine vellus-like hairs or that there is a 20% decrease in the actual diameter of each of the terminal hairs?

A: Miniaturization is the decrease in hair shaft length and diameter that results from the action of DHT on healthy, full thickness terminal hairs. The hairs eventually become so small that they resemble the fine, vellus hair normally present in small numbers on the scalp and body. Miniaturized hairs have little cosmetic value. Eventually miniaturized hairs will totally disappear. Twenty percent miniaturization refers to the observation, under densitometry, that 20% of the hairs in an area show some degree of decreased diameter.

In the evaluation of candidates for hair transplantation, we use the 20% as a rough guide to include all hairs that are not full thickness terminal hairs. Of course we are most interested in the presence of intermediate diameter hairs – i.e. those whose diameters are somewhere between terminal and vellus and are clearly the result of DHT. I don’t know if one can tell the difference on densitometry between vellus hairs, fully miniaturized hairs and senile alopecia. The partially miniaturized population is most revealing.

Miniaturization in the recipient scalp (i.e. the balding areas on the front top and crown that we perform hair transplants into) is present in everyone with androgenetic hair loss. Miniaturization in the donor area, however, is less common (in men). It means that the donor area is not stable and will not be permanent. Men with more than 20% of the hair in the donor area showing miniaturization are generally not good candidates for hair transplant surgery.

Topic: Hair Loss

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Posted by Robert M. Bernstein M.D. at 6:21 am

Why Should Hair Transplant Doctor Measure Miniaturization in Donor Area Before Transplant?

November 17th, 2006

Q: Why should a doctor measure miniaturization in the donor area before recommending a hair transplant?

A: Normally, the donor area contains hairs of very uniform diameter (called terminal hairs). In androgenetic hair loss, the action of DHT causes some of these terminal hairs to decrease in diameter and in length until they eventually disappear (a process referred to as “miniaturization”). These changes are seen initially as thinning and eventually lead to complete baldness in the involved areas.

These changes affect the areas that normally bald in genetic hair loss, namely the front and top of the scalp and the crown. However, miniaturization can also affect the donor or permanent regions of the scalp (where the hair is taken from during a hair transplant). If the donor area shows thinning, particularly when a person is young, then a hair transplant will not be successful because the transplanted hair would continue to thin in the new area and eventually disappear. It is important to realize that just because hair is transplanted to another area, that doesn’t make it permanent – it must have been permanent in the area of the scalp it initially came from.

Unfortunately, in its early stages, miniaturization cannot be seen with the naked eye. To detect early miniaturization a doctor must use a densitometer, or an equivalent instrument, that magnifies the surface of the scalp at least 20-30 times. This enables the doctor to see early changes in the diameter of the hairs that are characteristic of miniaturization. If hairs of varying diameter are noted (besides the very fine vellous hairs that normally occur in the scalp), it means that the hair is being affected by DHT and the donor area is not truly permanent.

In this situation, a person should not be scheduled for hair transplantation. If the densitometry reading is not clear, i.e. the changes are subtle and the doctor is not sure, then the decision to have surgery should be postponed. By waiting a few years, it will be easier to tell if the donor area is stable. Having surgery when the donor area is miniaturizing can be a major problem for a patient, since not only will the transplanted hair eventually disappear, but the scar(s) in the donor may eventually become visible. This problem will occur with both follicular unit transplantation (FUT) and follicular unit extraction (FUE).

Topic: Donor Area

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Posted by Robert M. Bernstein M.D. at 7:43 am

What is Difference in Hair Cloning Techniques Studied by Aderans and Intercytex?

November 10th, 2006

Q: I know that both Aderans and Intercytex are doing research with cloning hair. Is there any difference in their approaches?

A: Aderans is using the “two-cell” approach. They feel that the best way to produce viable hair follicles is to use a combination of inducer cells and responder cells. Each would be multiplied separately and then injected together into the skin. The inducer cells are follicular fibroblasts and lie at the base of the hair follicle. The responder cells are keratinocytes. They feel that the combination of cells will have the best chance of producing clinically useful hair.

Intercytex prefers a one-cell approach. Their researchers feel that when the cultured inducer fibroblasts are injected into the skin there will be enough existing cells in the skin to produce a cosmetically viable hair. In their experimentation, Intercytex uses a new animal model, termed the “flap graft” model, that involves the implantation of cultured dermal papilla cells with keratinocytes placed under a flap on the back of hairless mice. Later the flap is exteriorized (turned over), allowing the hair to grow normally. Exactly how this will be applied to clinical use in humans is not clear.

A completely different view is held Dr. Ralf Paus at the University of Luebeck in Germany. He feels that there are already enough stem cells in the bald scalp and that the key to hair re-growth is to target key elements in the hair cycle. He feels that topically applied inhibitors of catagen (the resting phase of the hair cycle), exogen (the formation of an empty hair follicle), or inhibitors of the terminal-to-vellus transformation (the process of a hair shrinking in size under the influence of DHT and referred to as miniaturization) will the most effective way to go.

Finasteride and dutasteride are drugs that work in this way, but are clearly not very effective in stimulating new growth. He also feels that an anagen inducer, along the lines of a minoxidil-type medication has a better chance of success then the stem cell targeting strategies described above. In these cases one would, in a sense, rejuvenate dormant hair follicles rather than induce new ones to grow.

Topic: Hair Cloning

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Posted by Robert M. Bernstein M.D. at 3:23 pm





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