Evidence that chorionic gonadotropin has intrinsic thyrotropic activity

The thyrotropic and gonadotropic specific biologic activities of chorionic gonadotropin (hCG) as assessed by the mouse thyrotropin and prostate weight bioassays increased at least 5 fold during purification. The hCG generated from recombination of hCG subunits that were essentially devoid of both activities recovered thyrotropic as well as gonadotropic biologic activity. These data show that the substance with thyrotropic activity found in hCG preparations has physicochemical properties indistinguishable from those of hCG and therefore, these results strongly suggest that thyrotropic activity is an intrinsic property of hCG.