You see, itâs actually the distance from the subject. The focal length is an indicator of the distance from the subject: the images are all framed the same; differences arise because the focal length is getting longer (zooming in) as the camera moves further away from the subject.
Normal values range from 0.4 to 4.0 milli-international units per liter (mIU/L). 1  TSH values can vary during the day. It is best to have the test early in the morning.  Experts do not fully agree on what the upper number should be. Opinions vary from 2.5 to 4.0 mIU/L.
If TSH is normal, usually defined by a much too broad range, something close to 0.5-5.0, rather than the more reasonable 0.3-3.0, testing stops. If you want all three tested, the doctor must individually order FT3, FT4 and TSH.