Does the Scalp Become More Sensitive to DHT as We Age?

Hi Doc. I just found it interesting that as we get past our 40s, Testosterone decreases gradually, yet people seem more prone to losing their hair by the age of 50 or so. Isn’t it true, testosterone levels and dht levels really have nothing to do with hairloss? It’s actually the scalp’s own sensitivity to dht?

For example, a man with high levels of both testosterone and dht can have a full head of hair, where as the man with low levels can be bald as a goose egg.

Response by Dr. Sharon Keene:

As chief medical officer for Dermagenoma, a company which manufactures and distributes a genetic test for androgen sensitivity, my esteemed colleague, Dr. Bill Rassman, asked if I would like to comment on the blog regarding the association between serum testosterone, DHT and hair loss especially as it applies to aging.

Dr. Rassman’s comments about the difference between genetics and the hormones of hair loss are right on target. First of all, the association between testosterone (T), dihydrotestosterone (DHT) and androgenetic alopecia (AGA) are indisputable…there are some people born without the enzyme to convert T into DHT, and these men have been observed to never develop male pattern baldness. The same observation has been made historically among twin brothers where one was castrated before puberty, and maintained a full head of hair in contrast to his brother who experienced male pattern baldness.

Since then there are many excellent studies which have documented the efficacy of the medications which are used today to treat AGA, such as finasteride, which blocks Type 1 5 alpha reductase and reduces the amount of DHT produced by the body. The fact that we notice different rates of hairloss in different families, and within families illustrates some of the genetic variability that exists among men who share this genetic trait.

Dr. Rassman mentioned androgen senstivity as being one of the many factors, and I agree, that is one of the genetic traits we have identified that seems to make a given person’s cells more responsive to their own hormones. This means that blood levels of a hormone can be the same between people, but response to the hormone can be very different, and even exaggerated in a person with greater sensitivity to their own DHT. At least 3 studies in men, and 2 in women have indicated response to anti androgen therapy, such as finasteride, as a treatment for hairloss is greater among patients who are more androgen sensitive. This is the premise behind the HairDx genetic test.

What I would add to this discussion is the fact that serum levels of hormones are no longer believed to necessarily reflect the activity level of T and DHT in androgen target cells. In the past decade, evidence has emerged that cells are able to create their own T and DHT from cholesterol, and metabolize it down to by products which are excreted, so that the T and DHT inside the cells are never seen in the blood stream.

Medications, such as finasteride, appear to be able to impact DHT at the cellular level to protect the hairs or reduce their response to their genetic predisposition to miniaturize and stop growing. The fact that men in their older years appear more likely to have hair loss may simply be the fact that it can take many years of gradual hair loss for the appearance of baldness or thinning to emerge, and is probably more a reflection of the fact that one must lose a great deal of hair before it is visible.

Nevertheless, there does not appear to be much protection against hair loss as men age and serum T levels fall, and this may be due to an as yet undetermined genetic time clock, but also because the androgen target cells are able to produce this hormone inside themselves in what is called an ‘intracrine’ fashion, even when the ‘endocrine’ hormones, those produced by the testes and adrenal gland, diminish. As long as the cell can produce DHT, and among those more sensitive to it and genetically predisposed, hair loss will likely progress in the absence of therapy.

Sharon Keene, M.D.
Chief Medical Officer Dermagenoma