ABSTRACT
Background: Discrepancies in the sensitivity to biological effects of the androgens, exerted through the binding of the hormone to the androgen receptor (AR), may also be involved in the inter-individual variation of T as well as in age related decline. The human androgen receptor (AR), located on chromosome Xq11-12, is a transcription factor regulating the development of male reproductive organs in the fetus and secondary sex characteristics at puberty in response to testosterone (T) and 5a-dihydrotestosterone (DHT). The AR contains two polymorphic regions, the (CAG)nCAA repeat encoding polyglutamine, and the (GGT)3GGG(GGT)2(GGC)n repeat encoding polyglycine, commonly referred to as the CAG and GGN repeats respectively. The aim of this study is to investigate the effect of the human androgen receptor genes CAG and GGN repeat polymorphisms in relation with androgen level.Materials and Methods: Sample collection: 180 male, the medical data of these volunteers were obtained and determined some androgen hormones at first phase of study in 2010-2011 (total testosterone (TT), free testosterone (FT) and bioavailable testosterone (BAT)). To determine CAG/GGN repeats length in exon of androgen receptor gene, using frozen serum as a source of deoxyribonucleic acid (DNA). DNA was extracted from blood samples (200 ml) using High PurePCR Template Preparation Kits.Results: The 180 men whose age is at least 40 were involved in our research and their average age was 55.1±10.3. The 46.7% (84) of the participants presents CAG gene, the 6.1% (11) of the participants presents GGN gene while the 25.5% (46) of the participants presents both CAG and GGN genes. However, the 21.7% of 39 men not presents CAG and GGN genes.Conclusion: The free testosterone level was significantly decreasing with aging. However, the appearance of CAG gene polymorphism was significantly higher in more aged people. Decline of free testosterone level in participants with CAG and [CAG+GGN] combined form was stronger than in people with GGN gene polymorphism and CAG, GGN both undetected people. But the level of bioavailable testosterone was decreasing with aging and the appearance of CAG gene polymorphism (r=-0.425, p=0.01) and [CAG+GGN] combined form (r=-0.491, p=0.028) was also increasing.