Hi, Thank you for your query. I can understand your concerns. If there is no residual thyroid function, the daily replacement dose of levothyroxine (Synthroid) is usually 1.6 mcg/kg body weight (typically 100–150 mcg). Since you have undergone throidectomy for cancer ,you need higher replacement doses (determined by TSH level monitoring). Thyroglobulin levels should be undetectable or very low after the surgical removal of the thyroid (thyroidectomy) for thyroid cancer. If the level of thyroglobulin is low for a few weeks or months after surgery and then begins to rise over time, then the cancer is probably recurring. Lack of certain vitamins and minerals can cause thyroid deficiency and if you have thyroid deficiency, the vitamins you are taking in are unable to be processed properly. If you are low on Vitamin A, your ability to produce TSH is limited. This vitamin is required by the body to convert T4 to T3. Vitamin A supplements along with protein helps. Vitamin B Complex:all the B vitamins are vital for good thyroid function. Vitamin C:the thyroid gland needs this vitamin to keep it healthy. Vitamin D:this vitamin when taken with thyroid hormone,counteracts the usual rapid excretion of calcium, and thus osteoporosis can be avoided. recommended dose 2,000 IU of vitamin D daily. Regards Dr. T.K. Biswas M.D. Mumbai