By Jan Nelson MSN, NP-C, ABAAHP
If you have been told “your thyroid is within normal limits”, but you are still feeling tired, depressed, you’ve gained some weight that just won’t come off, having a hard time warming up, these could be some of the many symptoms of hypothyroidism. Checking a TSH or free T4 does not give a true picture of what is really going on with your thyroid function. Free T3 is the active part necessary for the cells to function properly. T4 (thyroxine) and T3 (triiodothyronine) are important thyroid hormones. Yet, even with normal levels of T3 and T4, it’s possible to still have the symptoms of hypothyroidism, which may be due to excessive production of rT3 in the body. Reverse T3 competes with T3 at important binding sites, which is a problem because rT3 is inactive and therefore not as beneficial as T3.
Both thyroid hormone levels gradually decline with age: T4 decreases approximately 10-20% from age 25 to 75 and T3 decreases by 25%.
Some of the symptoms of inadequate conversion of T4 to T3 are: depression, weight gain, constipation, headaches, brittle nails, rough and dry skin, menstrual irregularities, fluid retention, poor circulation, diffuse hair loss, slow speech, anxiety or panic attacks, decreased memory, cold hands and feet. These are just a few, however, not all patients need thyroid medication. There are some factors that cause decreased production of T4, these include deficiency of zinc, copper, vitamins A, B2, B3, B6 and C. A good multivitamin can help with this.
The conversion of T4 to T3 requires an enzyme called 5’diodinase in sufficient quantities. Factors that can affect 5’dioiodinase production include: selenium deficiency, stress, cadmium, mercury and lead toxicity, starvation, inadequate protein intake high-carbohydrate diet, elevated cortisol levels, chronic illness and decreased kidney or liver function. Medications such as beta-blockers, birth control pills, estrogen, lithium, phenytoin, theophylline, and chemotherapy can also affect conversion. As with many other hormones in the body, diet will also interfere with a T4 to T3 conversion if not well balanced and healthy.
Replacement with T4 and T3 is typically preferable as it seems to work better and has a better tolerance. We use Armour Thyroid or a compounded T4/T3. These medications achieve better T3 tissue levels in the blood and target tissues i.e., heart, lung, spleen, muscle, adrenals, and ovaries. T3 is the active hormone in target cells, not T4. It is the dominant thyroid hormone in all body cells with a five times greater distribution volume than T4. Levothyroxine (T4) is also used to increase T4 levels, if conversion is a problem Cytomel (T3) SR can be added.
After thyroid replacement has been started the first improvements emerge during the second month with continued improvements in third and fourth months. Some people quickly feel improvement after two weeks or within a few days. Signs, symptoms and labs should be checked in 6-7 weeks to monitor for dosage adjustments.
As with all hormones, adequate testing along with attention to symptoms and health history are paramount to a final diagnosis and treatment. Your hormonal symphony requires an optimal thyroid function to stay in tune. Treatment of thyroid dysfunction should be individualized and customized to each patient.