The two thyroid hormone receptor genes have opposite effects on estrogen-stimulated sex behaviors

The two genes coding for thyroid hormone receptors (TR) alpha 1 and beta ha ve opposite effects on female sex behaviors. Deletion of TR alpha 1 reduced them, whereas deletion of TRP actually increased them. These results could not be attributed to altered levers of hormones in the blood, general alte rations in estrogen responsiveness or altered general activity. Instead, th ey indicate a previously unknown molecular mechanism upon which the two TR genes exert opposite influences.