Is the dukan diet effective for weight gain from hypothyroid? How do I go about this diet?

Avoid. This is just another money making diet program without any real benefit. It may help your wallet lose weight, but that's all. If you're hypothyroid you need to be on the correct dose of brand name T4 replacement. After that's done, it just eating less than you burn off in order to lose weight -- just as if you never had a thyroid problem.