Photoperiodic regulation of thyroid responsiveness to TSH inFundulus heteroclitus

Treatment of the killifish, Fundulus heteroclitus, with ovine thyrotropin produced elevations in serum thyroxin that varied seasonally with a strong inverse correlation to environmental photoperiod

E. Gordon Grau; Christopher L. Brown; Milton H. Stetson

2005

Scholarcy highlights

  • Treatment of the killifish, Fundulus heteroclitus, with ovine thyrotropin produced elevations in serum thyroxin that varied seasonally with a strong inverse correlation to environmental photoperiod
  • Similar rates of clearance of T4 in summer and winter suggest that an alteration in thyroid response to oTSH accounts for this change
  • Fish exposed to a short artificial photoperiod for one month responded to oTSH with T4 levels about twice as high as those in fish exposed to long days
  • On the other hand the T4 response to oTSH was sharply reduced at 5°C from that seen at 20°C
  • Photoperiodic induction of changes in thyroid sensitivity may aid in the maintenance of basal T4 levels under changing thermal conditions

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