What are the sleep characteristics associated with rising AM testosterone levels?
There is accumulating evidence in adult men that the testosterone profile is significantly influenced by NREM–REM cycling. Sleep architecture, characteristics which is associated with a nocturnal rise in am testosterone, as follows: (1) duration of the first NREM period; (2) daytime recovery sleep; (3) habitual sleep duration. Restriction of sleep to 5 hours/night for just 5 consecutive nights decreases am serum testosterone levels up to 15% and one night with no sleep or sleeping only 4.5 hours in the first half of the night decreases am testosterone levels by 20%. These facts argue for assessing sleep habits of patients in the workup for hypogonadism (see last question of the chapter on taking sleep history).