Apparently it has to do with a repeating sequence of DNA in the Androgen Receptor gene. The more a particular sequence repeats, the less effective Finasteride will be for you!
I wonder whether this can be applied to the medical practice, whereby a doctor can let you know in advance whether Finasteride will be effective for you based on some kind of DNA test.
Abstract:
Journal of Investigative Dermatology Symposium Proceedings
Effectiveness of Finasteride on Patients With Male Pattern Baldness Who Have Different Androgen Receptor Gene Polymorphism
Kazuhiro Kobayashi, Nagaoki Wakisaka, Yuh-ichi Taira, Masahiro Ishikawa, Yoshio Nakamizo,
Masashi Uwabu, Yasutaka Fukuda, Yasuyuki Taguchi, Takanori Hama, and Masaya Kawakami
NPO Future Medical Laboratory, Tokyo, Japan
Objectives: Most of male pattern baldness (MPB) patients have androgen-dependent trait although it is under the control of multiple genes, such as genes for androgen receptor (AR), IGF-1 and dihydrotestosterone regulations. A 5 alpha-reductase inhibitor, finasteride, is effective on MPB although there is a variation in the efficacy of this drug among the MPB patients. From the functional mechanism of this drug, it is thought to be effective on MBP caused by hyper-function of AR. Association of polymorphism in the first exon of AR gene with MPB has been demonstrated by some authors (Sawaya and Salita, 1998; Ellis et al,
2001).We have found that there is a correlation between the symptom level of MPB and the CAG and GGC repeat length in AR gene. To investigate relationship between the effectiveness of finasteride and the AR gene polymorphism, we determined the number of triplet repeats in AR gene of patients.
Methods: Blood cell DNA was extracted from 740 MPB patients (1962 y) and 54 non-bald men (4472 y). After PCR of the first exon of AR gene, the number of CAG and GGC triplets was determined by conventional sequencing or transcriptional sequencing method. AGGCCT sequence was determined using two different Stu I restriction enzymes.
Results and Conclusions: Effectiveness of finasteride in each patient was expressed as the improvent point of symptom derived from Hamilton-Norwood typing. Number of the triplet repeats (CAGGGC) was plotted against the symptom points. There was a broad correlation between these variables. Finasteride was more effective for the improvement of MPB in patients with shorter triplet regions of AR gene. These cases may be caused by hyperfunction of AR. On the other hand, this drug was less effective in certain cases with longer triplet repeats. They are thought to result from non-androgenic mechanism. This sort of analysis may help the drug choice for MPB patients.