During which stage of sleep is growth hormone secretion MAXIMAL, and what EEG pattern characterizes this stage?

• A REM sleep; low-amplitude, mixed-frequency (sawtooth) waves
• B N3 (slow-wave) sleep; high-amplitude delta waves (0.5–4 Hz) comprising >20% of epoch ✓
• C N2 sleep; sleep spindles (12–14 Hz) and K complexes
• D N1 sleep; vertex sharp waves and theta activity (4–8 Hz)

Explanation

Growth hormone secretion is tightly coupled to the first episode of N3 (slow-wave) sleep, which occurs within the first 90 minutes of sleep onset. N3 is defined by delta waves (0.5–4 Hz, >75 µV amplitude) occupying more than 20% of a 30-second epoch. This is the dominant pulse of GH in adults. REM sleep shows a desynchronized EEG with sawtooth waves and is not associated with GH release. N2 is characterized by sleep spindles and K complexes; N1 by theta waves and vertex sharp waves.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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