24 HOUR PROFILES OF 4 HORMONES UNDER CONSTANT ROUTINE

We studied the circadian features of melatonin, cortisol, thyroid stim ulating hormone (TSH), and growth hormone (GH) together with rectal te mperature during 36 h continuous forced wakefulness without physical e xercise under dim light condition (constant routine). Subjects consist ed of four healthy men aged 22-24 years. Blood sampling was conducted hourly, and food and water were supplied bi-hourly during the constant routine. Melatonin, TSH and cortisol displayed clear circadian rhythm s under constant routine condition. While GH secretion was unlikely to be driven solely by the circadian pacemaker, its suppression round BT nadir may indicate that GH secretion was modulated to some extent by circadian rhythm.