Seasonal Variations of Glucose and Triiodothyronine Concentrations in Serum of Carp (Cyprinus Carpio L)

Summary

Thyroid hormone and glucose serum concentrations (SC) of carps (Cyprinus carpio L) have been monitored at weekly intervals throughout the year. T₄ and rT₃ concentrations were always below the limit of detection of the assays applied. T₃ and glucose mean SC showed seasonal variations. Highest T₃ SC were reached in summer with a peak value in August and lowest values in winter with a maximum in December. Glucose SC have been found to be highest in winter and lowest in summer. Statistical analysis showed a negative correlation between T₃ and serum glucose SC (r=-0.77, P < 0.001). The seasonal dependency of T₃ and glucose SC suggest that either temperature, food intake or day-light or both might play a role in the regulation of glucose metabolism as well as of T₃ production or metabolism.

Key-Words

Thyroid Hormones - Glucose Metabolism - Seasonal Variations - Carp