Effect of increased circulating corticosterone on serum and thyroidal concentrations of iodothyronines and the responses to thyrotrophin in the immature fowl (Gallus domesticus).
Four-week-old fowl were given subcutaneous implants containing a mixture of corticosterone: cholesterol (1:4, w/w) to raise serum corticosterone concentration. The effects on circulating thyroxine (T4), triiodothyronine (T3), and reverse T3 (rT3), thyroidal T3 and T4 and responses to thyrotrophin (TSH) were examined. Increased circulating corticosterone caused an increase in the plasma concentration of T4 and a decrease in T3 and rT3 indicating reduced extrathyroidal 5 and 5' monodeiodination of T4. After single injections of 0.1 IU TSH/kg body weight were given 3 and 13 days after corticosterone implants there was an increase in the T3 response and a delay and reduction in the T4 response. This may have been due to a corticosterone-induced increase in the synthesis of T3 relative to that of T4. Although the relative increase in thyroidal T3 concentration was greater 3 days after corticosterone implants were given, no significant shift in the T4:T3 ratio in the thyroid glands was observed.
D000818:Animals; D002645:Chickens; D003345:Corticosterone / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D004343:Drug Implants; D005260:Female; D008297:Male; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism; D013963:Thyroid Hormones / Q000097:blood / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology*; D013974:Thyroxine / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism; D014285:Triiodothyronine, Reverse / Q000378:metabolism
D004343:Drug Implants; D013963:Thyroid Hormones; D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013972:Thyrotropin; D013974:Thyroxine; D003345:Corticosterone