"Low thyroid" is shorthand for low levels of the thyroid hormones thyroxine and triiodothyronine. This condition is called hypothyroidism. These hormone levels might be low for many reasons, one of which is lack of iodine. In some rare instances, doctors might prescribe potassium iodide, or iodine tablets, to treat some thyroid problems. You should never try to self-diagnose or self-treat thyroid problems because hypothyroidism has many possible causes, most of which are not treated with potassium iodide.
Thyroid Hormones
The pituitary gland makes thyroid-stimulating hormone, or TSH, which acts as a messenger, directing the thyroid to make thyroxine and triiodothyronine. Thyroxine is called T4 because a molecule of this hormone has four iodine atoms. Triiodothyronine is called T3 because it has three iodine atoms. Often, these hormones are lumped together and called "thyroid hormone."
Feedback Loop
TSH, T3 and T4 form a feedback loop. In healthy people, the pituitary gland stops secreting TSH when the body has sufficient levels of T3 and T4 and secretes more THS when levels of T3 and T4 are too low. If thyroid hormones are low, PubMed Health reports, doctors often replace the thyroid hormone that is lacking. Synthetic hormones, such as levothyroxine, might be prescribed instead of potassium iodide.
Potassium Iodide
Potassium iodide is available where most vitamins are sold. Often it is referred to as "iodine" or "iodine tablets." MayoClinic.com explains that while some alternative practitioners recommend iodine tablets or kelp supplements to treat hypothyroidism, lack of iodine is rarely the cause of this condition.
Daily Requirements
Adults need 150 micrograms of iodine per day. Given that a single gram of salt provides 77 micrograms of iodine, and most people consume several grams of salt per day, iodine deficiencies are almost unknown in the U.S. Other sources include milk, codfish, shrimp and fish sticks. It is possible that strict vegans who are on extremely low-salt diets might not get adequate iodine. For these people, supplementation might be necessary to treat hypothyroidism. Supplementation should not exceed the daily requirement because excess iodine intake is linked to thyroid hormones.
