Circannual rhythm of plasma thyrotropin in middle-aged and old euthyroid subjects

Manuela Simoni, A. Velardo, V. Montanini, M. Faustini Fustini, S. Seghedoni, P. Marrama

Research output: Contribution to journalArticlepeer-review


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 (fT4) or ambient temperature in any group. Moreover, plasma fT4 did not show seasonal variations.

Original languageEnglish
Pages (from-to)184-189
Number of pages6
JournalHormone Research in Paediatrics
Issue number5
Publication statusPublished - 1990


  • Ageing
  • Circannual rhythm
  • Free thyroxine
  • Thyrotropin

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism
  • Pediatrics, Perinatology, and Child Health


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