Rodney Sinclair, MBBS, FACD, MD.
University of Melbourne, Fitzroy, Australia.
SUMMARY of Dr. Sinclair’s Abstract from his presentation at the International Society of Hair Restoration Surgery, 2005 – Sidney, Australia
Twin studies have confirmed the strong heredity of androgenetic alopecia. The purpose of the present study is to explore the genetic basis of androgenetic alopecia by gene analysis. The study compared the sequence of several candidate genes between groups of individuals considered to be most and least genetically predisposed to androgenetic alopecia. Most likely are young males who already have a significant degree of baldness and least likely are those who are older and have no sign of hair loss.
The 5 alpha-reductase genes (SRD5A1 and SRD5A2), aromatase genes, Y chromosome and androgen receptor genes were analyzed. The authors found a significant difference in the frequency of a single base change in the coding region of the AR gene. These results provide good evidence for the involvement of AR in androgenetic alopecia.
Interestingly, 77% of non-bald men carry the version of the AR gene found in bald men. This suggests that the AR gene is necessary but not sufficient for causing baldness. This raises the possibility that other genes are acting in conjunction with AR. For instance, genes other than SRD5A1 and SRD5A2 that control levels of DHT production remain candidates. Given that 5 alpha-reductase is increased in balding scalp, these might include transcription factor genes which regulate the production levels of 5 alpha-reductase. Such transcription factor genes are yet to be identified. The many other genes, known and unknown, that are involved in androgen production, regulation and response may also be involved.
In addition to androgen-related genes, genes involved in patterning, signaling and hair follicle morphogenesis are other potential candidates for future research.Posted by