Seasonal testosterone profile and testicular responsiveness to pituitary factors and gonadotrophin releasing hormone during two different phases of the sexual cycle of the frog (Rana esculenta).

Plasma and testicular testosterone concentrations in the frog, Rana esculenta, were studied by radioimmunoassay and showed similar seasonal fluctuations. The increase in testicular androgen during November preceded that occurring in the plasma by 2 months. Pituitary products and gonadotrophin releasing hormone, and the responsiveness of the testis to these substances play an important role in determining the hormone profile.