Testosterone Levels in Relation to Oral Contraceptive Use and the Androgen Receptor CAG and GGC Length Polymorphisms in Healthy Young Women

In a 2006 study involving 258 healthy young women from high-risk breast cancer families, it was found that oral contraceptive (OC) users had significantly lower testosterone levels than non-users, particularly during menstrual cycle days 5-10. The study also discovered that women with a greater number of long GGC alleles in the androgen receptor gene had even lower testosterone levels when using OCs during these days. This effect was not seen in non-users or during other cycle days. Furthermore, women with two short GGC alleles had a higher incidence of breast cancer, suggesting a potential link between the short GGC allele and increased breast cancer risk after OC exposure. The study concluded that the GGC repeat length is a significant genetic factor that modifies testosterone levels in OC users and may be associated with breast cancer risk, while the CAG repeat length and BRCA mutation status did not show an association with testosterone levels or breast cancer risk in this context.