How do you decide when to evaluate for central hypothyroidism in a patient with low-normal TSH and low free T4?

The differential in these patients is 1) mild subclinical hyperthyroidism 2) central hypothyroidism 3) normal variant related to assay detection limitations.

It would be important to obtain a good history and try to identify any hypothyroid or hyperthyroid symptoms. Having said that, patients will u...

First, you need to consider if there are physiological reasons or a low-normal TSH, including minimal excess thyroid hormone, or euthyroid sick. Next, you need to consider other causes for a low Free T4. The free T4 can appear to be lower than normal when there is an abnormally low thyroid hormone-b...