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      Circannual Rhythm of Plasma Thyrotropin in Middle-Aged and Old Euthyroid Subjects

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          The circannual rhythm of plasma thyrotropin (TSH) was evaluated in 8,310 euthyroid, serially independent, young, middle-aged and old men and women. A statistically significant circannual rhythm of plasma TSH was validated, by the mean group-cosinor method, in the middle-aged and old men and women (p < 0.05), with acrophase in December, whereas the young subjects did not show any rhythm. No significant correlation was found between TSH plasma levels and free thyroxine (fT<sub>4</sub>) or ambient temperature in any group. Moreover, plasma fT<sub>4</sub> did not show seasonal variations.

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          Hormone Research in Paediatrics
          S. Karger AG
          02 December 2008
          : 33
          : 5
          : 184-189
          Department of Endocrinology, University of Modena, Modena, Italy
          181506 Horm Res 1990;33:184–189
          © 1990 S. Karger AG, Basel

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          Pages: 6
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