Testosterone dive baffling
The overall testosterone level of American men has fallen steadily during the past two decades - and researchers don't know why. Neither ageing nor health factors such as smoking or obesity fully explains the decline, discovered by New England Research Institute's analysis of blood from about 1,500 men over 45 years old during three periods since 1987. Testosterone is the primary male sex hormone and helps maintain bone and muscle mass, healthday.com reports. Low levels have been linked to problems such as low libido and diabetes.