Because TSH controls the body’s T3 and T4 hormones, getting your TSH levels measured with a blood test can be helpful for determining how your thyroid is functioning. It may sound counterintuitive, but high levels can indicate an under-active thyroid, while low levels can indicate an overactive thyroid. This is because when you have an underactive thyroid the thyroid hormones T3 and T4 are low, and so the body responds by increasing TSH to stimulate T3 and T4 production. The opposite happens in the case of an overactive thyroid.

To find out additional facts about how TSH levels affects your health, both good and bad, you can read the full article by Joe Cohen here: