Effects of Stimulated Adrenocortical Activity on the Concentration of Thyroxine and Triiodothyronine in Blood Serum of Piglets

Summary

The effects of elevated adrenocortical activity, induced by cold exposure, weaning or starvation, or exogenous adrenocorticotrophin (ACTH) on the concentrations of thyroxine (T₄) and triiodothyronine (T₃) in blood serum were investigated in 99 sucking piglets and weaners, divided into five experiments. No changes in concentrations of circulating iodothyronines were recorded during a 3-hour exposure of 3- to 4-day-old piglets to ambient temperature of 8—12 °C. Two days after weaning of 4-week-old piglets the concentration of T₄ increased. At the same time a decrease of the concentration of T₃ was observed in their starving litter mates. Two hours after the administration of ACTH, the concentration of both iodothyronines decreased, that of T₄ nonsignificantly. 17 hours after the administration of the second of two doses of ACTH, i.e. at the time when the concentration of corticosteroids approached initial values, the blood concentration of iodothyronines both in sucking piglets and in weaners was elevated, that of T₄ nonsignificantly. We suggest that for the changes of T₄ and T₃ concentrations in blood sera of stressed animals both specific stressor effects and circulating corticosteroids are responsible. The suppressive action of corticosteroids seems to be limited to the period of adrenocortical stimulation only.

Key words

Stress - ACTH - Corticosteroids - Thyroid hormones - Pig