Chapter 59, Goodman & Gilman, 9th ed.
Senescence: As men age, the serum testosterone concentration gradually decline and the sex hormone-binding
globulin concentration gradually increases, so that by the age of 80 the total testosterone concentration is approximately
85% and the free testosterone is approximately 40% of those age 20. This
reduction in serum TTT contributes to decreases in energy, libido, and muscle mass.
These conclusions are supported by changes in younger men with hypogonadism.
In women the
loss of androgen secretion causes a decrease in sexual hair, but not for many years.
Testosterone replacement in androgen-deficient women will improve their libido, energy, muscle mass and strength, and
bone mineral density.
levels of serum TTT is 500 to 700 ng/dl in men, 30 to 50 in women. Based on this
100 mg of the TTT gel produces a level averaging 800 mg for all 24 hours in hypogonadal men, while the 10 mg patch after 12
hours falls below 600 mg, and is at 500 at the end of 24 hours. When the TTT
gel is used, there is no appreciable fluctuation during the course of the day, but steady-state values may not be reached
for a month after the initiation of treatment. Normalization of the serum TTT
concentration results in normal virilization in men who are not normally virilized and maintence of virilization in those
who are. Libido and energy in hypogonadal men should increase within a few weeks. Moreover, there are no side effects as long as the dose is not excessive.