Hi i am Dr Ahmed Aly thanks for using healthcaremagic site , I had gone through your question and understand your concerns .. In my opinion yes i think its the cause of your severe leg cramps but indirectly as alot of studies say that it decreases the bone density and thus alters serum calcium and other minerals . For now i suggest some lab investigation to diagnose mineral level in blood for proper evaluation and management , However, estrogen use appeared to negate the adverse effects of thyroid hormone on bone mineral density. I think you may need to decrease dosing or ask your endocrinologist for the best alternative for your case that suits your body requirements . Please click THANK YOU and consider a 5 star rating with some positive feedback if the information was helpful. Hope the above information helps you, Any further clarifications feel free to ask.