Thyroid blood tests help figure out how well your thyroid gland is working. TSH helps the thyroid gland know when to make more thyroid hormones. Free T4 is the type of hormone that becomes active when ...

In 1 year of thyroid function tests across Wales, the incidence per 100,000 population of low free T4 (FT4) was 98-301, whereas that of central hypothyroidism was just two. With the current increased ...