I request serum T4 (the main hormone produced by the thyroid), free T3 (the biologically active thyroid hormone at the cellular level) and a thyroid stimulating hormone (TSH) level. The T3 level inside the cell correlates very well with the free T3 that is in the serum. Following orthoiodosupplementation, serum T4 and TSH levels usually go down and free T3 stays steady . I have seen TSH sometimes go up rather than down while T4 and free T3 did not change or may have gone up some. This does not mean that the patient was developing hypothyroidism but that the brain was stimulating the body to make more sodium Iodide symporters (NIS). The NIS are channels in the cell membrane that transport atoms into a cell as compared to a calcium channel or a sodium channel or a chloride channel where the channel only admits one atom to go through. The NIS transports sodium Iodide into cells and has been found in all cell lines tested so far. Thyroid stimulating hormone, prolactin and oxytocin have been found to stimulate the making of NIS . While taking iodide, one may see an elevated TSH but we have to recognize that this is not a bad thing. TSH has many actions outside the thyroid that have been discovered . While taking iodine, the vast majority of patients lose fat and gain muscle weight . Very rarely has weight gain occur. Often a check of the patientís T4, free T3 and TSH shows the T4 to go down, free T3 going down and TSH going up. Iodide is an essential nutrient that is absorbed by all cell lines. Its highest concentration is seen in the thyroid.