Test levels begin to decline in the late third or early fourth decade and diminish at a constant rate thereafter. Steeper declines occur in an unbound or free test. Lower testosterone levels are a major risk factor for a multitude of metabolic and mental health conditions. Travinson, et al. (2007) recently published an alarming study showing that testosterone levels have dropped about 1.2% per year, or about 17% overall, from 1987 to 2004 at an accelerated rate in American males as compared to previous periods. Recent studies have also shown that SHBG (Sex Hormone Binding Globulin) levels have increased, further exacerbating the situation.