Reciprocal interactions between testis and thyroid in male Japanese quail

Abstract

The effects of castration or thyroidectomy, and of testosterone and thyroxine (T 4) administration on plasma testosterone and thyroxine concentrations were studied in quail kept under either experimental short days (6L-18D) or long days (18L-6D). Thyroidectomy or treatment with T 4 did not affect the basal concentration of testosterone in nonphotostimulated quail, but induced a strong inhibition of testis growth and reduced plasma testosterone concentrations in photostimulated quail. On the other hand, exposure of intact quail to long days, or testosterone administration to castrates under short days, induced a decrease in plasma T 4, while exposure of castrates to long days increased plasma thyroxine. These results are in favor of an inhibitory reciprocal interaction between androgenic and thyroid function in quail. In addition they seem to point to a stimulatory effect of long days per se on thyroid function in quail.