It decreases faster than total testosterone; by about 50 % in healthy men from the ages of 25 to 75. (hghinjections.us)
A group of healthy men were fed a meal high in saturated fat, blood samples were taken, and results showed that after the meal, total and free testosterone levels dropped significantly. (mindbodygreen.com)
For example, in one study healthy men who took testosterone medications increased muscle mass but didn't gain strength. (mayoclinic.org)