How does aging change hormonal release?
- Changes to sleep architecture with aging are thought to lead to hormonal changes. Normal aging is associated with loss of SWS and REM, with increased sleep fragmentation.
- Recall that GH and PRL rise primarily in relation to the SWS of NREM, whereas TSH, cortisol, and testosterone increases are primarily under circadian control. In younger men, there is a dose-response relationship between SWS and GH secretion.
- For example, in 16- to 25-year-old males, SWS is nearly 20% of the sleep period and tails off to 5% to 10% at age > 40 years. This is associated with GH secretion during sleep of ∼350 mcg in the 16- to 25-year-old, but not > 100 mcg in individuals age > 35 years.
- Most of the PRL released during a 24-hour period is during sleep regardless of gender; there is nearly a 50% decrement in nocturnal PRL secretion with aging. The extent of circadian changes in cortisol and TSH are less dramatic with aging. Day–night TSH fluctuations also dampen with age.
