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There is much more to a thorough thyroid evaluation that performing a TSH Test, yet your typical doctor will only test for Thyroid Stimulating Hormone. Basic thyroid tests should include the 9 tests I discussed in my first blog “Comprehensive Thyroid Panel”. Yet even performing these is not enough to totally evaluate your thyroid problem. This blog will discuss 3 additional tests that are critical in understanding why your thyroid may not be functioning normally.
A very little appreciated reason your thyroid gland may not be producing enough thyroid hormone is that you simply don’t have enough of the building blocks to make it. Thyroid is a simple hormone, requiring only the amino acid tyrosine and 3 or 4 molecules of iodine. About 1/3 of the world’s population lives in iodine deficient areas, including people living in large parts of the United States. The RDA for iodine is only 150 micrograms. This may be sufficient to prevent most goiters but is not enough to provide optimal levels for all cells of the body.
Every cell in the body requires iodine. The best way to test to see if each cell has optimal levels is through an Iodine Loading Test. It is based on the concept that the normally functioning human body has a mechanism to retain iodine until it is fully supplied. Extra iodine will be excreted in the urine, so the less you excrete in the 24- hours after taking a 50mg. iodine pill, the greater the need for iodine.
Many functional hypothyroid conditions respond favorably to iodine supplementation, making the iodine-loading test an essential component of a comprehensive thyroid lab evaluation. (Warning: Excess iodine may actually inhibit the thyroid gland, so it is not recommended that you supplement until you are sure you need it).
Iron is another trace element that is essential to thyroid function. Most associate iron with blood. It is what makes blood red. A severe iron deficiency will cause anemia. Signs and symptoms of anemia include, fatigue, pallor, brain fog, increased heart rate, poor exercise tolerance, dizziness upon standing, leg cramps and restless leg syndrome, insomnia, cold hands and feet, and depression. Some of these symptoms are similar to hypothyroidism, and for good reason. The problem is that iron deficiency anemia is the end-stage of iron deficiency. The body will prioritize iron to provide it to red blood cells, at the expense of tissue iron stores, so you may not be anemic and still have an iron deficiency.
Iron is critical to thyroid function. It is necessary for the production of neurotransmitters that are needed by the brain to produce TSH, which then causes the thyroid gland to release thyroid hormone. The ultimate effect of thyroid hormone is to increase metabolism (energy or ATP). The majority of energy is produced in the mitochondria, which also requires iron.
Iron deficiency is shown to reduce T4 to T3 conversion, increase reverse T3 levels, and block the effect of thyroid hormone. T4 replacement will not work properly as thyroid replacement if iron deficiency is present. To determine if there are adequate stores of iron at the cellular level, an iron study is the best test.
No hormone exists in isolation. There are relationships between thyroid hormone and cortisol among others. Excess cortisol, which is common to those under stress, reduces the production of TSH, which then reduces the amount of thyroxine (T4) produced. T4 must be converted to the active thyroid hormone T3, which requires an enzyme. Elevated cortisol reduces this conversion, causing lower levels of the metabolically active T3 hormone. Even if you have “normal” T3 levels, cortisol can cause the thyroid receptors on the surface of every cell in the body to not recognize T3. If T3 binding to the receptor is inhibited, then it can’t get into the cell to turn on the genes that control metabolism. This is called “receptor-site resistance”.