Hi, dear I have gone through your question. I can understand your concern. You have hypothyroidism and you are taking thyroxine. Weight gain and cold intolerance is common in hypothyroidism. But the dosages of thyroxine replacement depends on your T3, T4 & TSH level. So go for thyroid function test and take treatment accordingly. Hope I have answered your question. If you have any doubts then feel free to ask me. I will be happy to answer. Thanks for using health care magic. Wish you a very good health.