Community-dwelling men , 65 years of age or older , with limitations in mobility and a total serum testosterone level of 100 to 350 ng per deciliter ( 3.5 to 12.1 nmol per liter ) or a free serum testosterone level of less than 50 pg per milliliter ( 173 pmol per liter ) were randomly assigned to receive placebo gel or testosterone gel , to be applied daily for 6 months .
