A properly functioning thyroid gland makes T4, (Thyroxine) hormone. T4 is considered a storage form of thyroid hormone that has to be converted into the active hormone T3 (Triiodothyronine). This important thyroid hormone controls your metabolism, energy level, mood, and the function of almost every cell in your body.
Synthroid, L-Thyroxin, and Levothyroxine are medications that only contain T4. Desecrated or glandular thyroid NP, Armour and compounded bioidentical thyroid contain both T4 and T3. Liothyronine is a synthetic T3.
Low thyroid function can occur from many things – especially a nutrient deficiency of iodine, which is pretty much absent in the typical American diet, or from toxic exposures to chemicals and heavy metals such as mercury, bromine, chloride. Some people are just poor “converters” not making enough T3 from their T4 especially if they're on a T4 only medication.
TSH (thyroid-stimulating hormone) goes up when thyroid hormones are low, and goes down when there is enough thyroid hormone in the body to function properly. It is an inverse relationship. The ranges for TSH go up to about 5, but optimal TSH is less than 1. By the time TSH is above 2-3, you are essentially hypothyroid.
Desecrated thyroid like NP or Armour has been a good alternative to using synthetic T4, until recently. For whatever reason, these thyroid medications have been recalled repeatedly due to inconsistencies in the dose, resulting in a lack of availability. Research has now shown that antigens (a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies) present in glandular medications can set off an autoimmune response especially for those with autoimmune diseases.
Compounded thyroid replacement offers a more tailored approach to treating underacting thyroid. Compounding allows the pharmacist and physician to work together in order to create a medication that is right for you. This includes adjusting the strength, ingredients, and formulation to fit your specific needs.