When I talk to my patients about thyroid issues I like to use the analogy of a mechanic looking at a car. Most doctors only check a TSH level. To me, this is like looking at the gas gauge and assuming that if there’s enough gas in the car, it’s going to run well. However, the thyroid system (as well as a car) is much more complicated. Your car may have plenty of gas in the tank but if the engine is missing it’s not going to get very far. Similarly, if one’s thyroid gland is producing optimal amounts of hormone but the rest of the system isn’t working well you’re not going to get too far. The thyroid system involves the conversion of T4 to T3. T3 is the most active form of hormone. It moves into cells and increases a wide variety of metabolic chemical reactions. Within the thyroid system, a number of things can go wrong. You may not convert T4 to an adequate amount of T3. There’s another hormone called reverse T3. It’s like the parking brake of the system. Your T3, T4, and your TSH could all be normal but if you’re producing too much reverse T3 the parking brake on your metabolism is still engaged and you’re going to be moving pretty slow. High levels of insulin seen in people with the metabolic syndrome can increase the conversion of the T4 to reverse T3. Other issues such as, non-optimal iron, high cortisol levels, and low iodine levels can also increase the conversion of T4 to reverse T3. Low cortisol levels can impair the ability of T3 to enter the cells also putting a brake on the system.
Even if your TSH level is normal, you may still have significant problems. I like to take a more complete look at the car to make everything is fine tuned.
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