A few months back, I read the BEST simple explanation about thyroid function and why checking only TSH and T4 is not enough. Most importantly, why TSH and T4 alone may not be the right way to choose treatment if medication is needed.
From the article “Understanding TSH, T4 and T3”, Leslie Bosswell explains that she views the system as a light you use to see. TSH is the switch. T4 is the light fixture. T3 is the light bulb.
The TSH test only tells you if the switch is in the “On” position. The Free T4 test measures storage thyroid function to determine if the light fixture has a light bulb in it. Only the Free T3 test measures active thyroid hormone to see if you have light to see by. If not enough light to see, that is hypothyroid symptoms.
“When only TSH and Free T4 levels are tested, the main function of the thyroid is left out, the T3 levels”. Given the impact that thyroid function has on brain development, digestive, heart and muscle functions, not fully examining its performance should NEVER be an option for a child with Down syndrome.
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