Frequently asked question: How is hypothyroidism diagnosed?

Problems with your thyroid gland can be diagnosed using blood tests. Tests are then done to see how much free T4 and TSH are present in your blood. If there is a problem with the thyroid gland itself, the free T4 will be too low and the TSH will be too high. If the problem is not the thyroid gland but instead the hypothalamus or the pituitary, for example, then the free T4 will be too low and the TSH will be too low, normal or just slightly increased.
If a problem with the hypothalamus or the pituitary is suspected, then measuring the levels of other hormones (such as cortisol and IGF-1) and a TRH test (to test the function of the pituitary gland) can provide more clarity.

Relevant medical information