As mentioned above, clenbuterol does not affect the thyroids directly, but it is a very unhealthy thing to use for fat loss. Clenbuterol, albuterol, ephedrine and T3/4 were never meant for fat loss, and the dosages needed for that will cause a lot of side effects. Additionally, the bad thing about clenbuterol is that it will also reduce your lean mass, not only fat, and that is not cool at all if you try to gain muscle mass. Instead, better opt for compounds that were specifically developed for such purposes, such as Cardarine GW-501516. It is a perfect recomp tool, as it will burn fat, and maintain lean mass without any side effects at all. Besides, it will greatly increase endurance and recovery, which is also very good when you try to do more cardio in order to lose fat.