NYCTHEMERAL PATTERNS OF THYROID-HORMONES AND THEIR RELATIONSHIP WITH THYROTROPIN VARIATIONS AND SLEEP STRUCTURE

In order to precise the relationships between TSH, FT3, and FT4 nycthe meral variations and the relationships between thyroid hormone variati ons and sleep, 8 healthy young males were studied twice, once during a 24-h experiment with normal nocturnal sleep, and once during a night of sleep deprivation. The subjects received continuous enteral nutriti on and remained supine during the whole experiment. Blood was sampled every 10 min for TSH, FT3, and FT4 measurements. Thyroid hormones exhi bited small oscillations which were not systematically related to TSH pulses, and there was no evidence of a nycthemeral rhythm. SWS was ass ociated with TSH declining phases, whereas awakenings were strongly as sociated with ascending phases of TSH variations. There was no associa tion between sleep structure or awakenings and thyroid hormones. Sleep deprivation led to increased TSH and FT3 levels, without any variatio n in FT4 levels. These results demonstrate that short-term thyroid hor mone variations do not only depend on the effect of TSH on thyroid sec retion but also on a possible role of TSH on peripheral FT4 to FT3 con version. Conversely, the relationships between TSH and SWS or awakenin gs are not mediated by thyroid hormones.