The sleep stages
Sleep cycles through:
- N1 (light sleep), transitional, brief
- N2 (light sleep), most of total sleep time
- N3 (deep / slow-wave sleep), physical restoration; mostly first half of night
- REM (rapid eye movement), mental processing, memory consolidation; mostly second half of night
Each cycle ~90 minutes. A typical night has 4-5 cycles.
Hormone release timing
- Growth hormone, peaks in deep sleep, particularly first 2-3 hours
- Testosterone, pulses during REM sleep
- Melatonin, rises before sleep, peaks during sleep
- Cortisol, rises in second half of sleep, peaks at waking
- Prolactin, rises during sleep
- Thyroid (TSH), peaks early sleep
Deep sleep and GH
Growth hormone release is concentrated in deep sleep. Suppressed deep sleep (from alcohol, sleep apnea, late food, etc.) crashes GH output. Total nightly GH largely depends on deep sleep quality.
Aging reduces deep sleep substantially, partly explaining the GH/IGF-1 decline with age.
REM and testosterone
Testosterone pulses during REM sleep. Suppressed REM (from alcohol, late screens, sleep apnea) reduces overnight T accumulation and morning peak.
What disrupts architecture
- Alcohol (suppresses REM, fragments sleep)
- Late screens / blue light (delays sleep onset, reduces deep sleep)
- Sleep apnea (fragments architecture, reduces both deep and REM)
- Late caffeine
- Late large meals
- Stress / cortisol elevation
- Inconsistent sleep timing
- Some medications
Architecture optimization
- Consistent sleep-wake timing
- Cool, dark, quiet environment
- Limit alcohol (especially close to sleep)
- Limit late caffeine
- Last meal 3+ hours before sleep
- Limit blue light evenings
- Address sleep apnea if present
- Magnesium supplementation often helpful
- Manage stress
Tracking sleep
- Wearables (Whoop, Oura, Garmin, Apple Watch) estimate sleep stages
- Look at deep and REM percentages, not just total time
- Aim for 1+ hour deep sleep, 1.5+ hours REM
- Track consistency across nights
- Sleep efficiency (time asleep / time in bed) above 90%
The clinical insight: Sleep duration without architecture is incomplete. 8 hours of fragmented sleep with suppressed deep and REM produces poor hormonal output. Architecture quality matters as much as quantity.
Bottom line
Hormones are released in specific sleep stages. Deep sleep drives growth hormone. REM drives testosterone pulses. Disrupted architecture compromises hormonal output independent of total sleep time. Optimization addresses both quantity and quality.