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Amphetamine, a clinically used sympathomimetic central-acting drug, was administered in Spansule capsules in a blind schedule to 8 normal obese volunteers in a daily (8 a.m.) single 15 mg dose for 7 days. The study, conducted in the metabolic ward, included two 7 day placebo periods (pre- and post-drug). During the 1st placebo period, all subjects exhibited within the 1st 2 h of sleep a clear and significant nocturnal increase of growth hormone (GH) closely related with sleep stages 3 and 4. Thyrotropin (TSH) increase was observed between 01.00 to 04.00 h and was accompanied by a reduction of thyroxine (T4) levels. Cortisol levels presented their characteristic rhythm, clearly associated with paradoxical sleep (REM). Amphetamine significantly reduced stages 3 and 4, as well as REM sleep, and increased stage 2. GH and cortisol circadian profiles were preserved, although their magnitude was diminished. The extent of nocturnal TSH and T4 changes was significantly reduced. Drug withdrawal was accompanied by a rebound of REM sleep and a trend to recover the pretreatment TSH and T4 temporal profile. These results suggest that adrenergic neurotransmitters may be a significant modulating system for TSH and cortisol, whereas GH nocturnal secretion may be influenced by different mechanisms.

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