Why do some men thrive on "normal" testosterone levels while others feel off? The answer might lie beyond your lab values, in your androgen receptor genes.
The androgen receptor (AR) is the protein that testosterone and DHT bind to in order to exert their effects. The sensitivity of that receptor is shaped in part by a stretch of repeating CAG sequences in the AR gene. Shorter CAG repeats generally mean a more sensitive receptor; longer repeats can mean your body needs more hormone to achieve the same effect.
This is why two men with identical total testosterone can have very different experiences with energy, libido, mood, and body composition. Understanding your AR-CAG repeat length adds a missing layer of context to hormone optimization, helping you and your clinician fine-tune a protocol around how your body actually responds, not just what the number says.
Marek's AR-CAG test is a one-time genetic test that reveals your receptor sensitivity, giving you data you can use for the rest of your life.