Timing of TSH Measurements

TSH (thyroid stimulating hormone) is the standard blood test that is used to screen for thyroid concerns.  In Canada, the range for TSH is .2 - 4.0 with a low TSH reflecting hyperthyroid function and a high TSH reflecting hypothyroid function.  An article by Tina Kaczor in the December 2012 issue of the Natural Medicine Journal reported on a study published in Endocrine Research in August 2012 that found a significant difference in TSH levels depending on the time of day the TSH was measured.  The study focused only on people with hypothyroid concerns (either autoimmune thyroiditis or primary hypothyroidism) and it found that both groups of people had lower (more balanced) TSH levels in the afternoon compared to the morning.  While it is encouraging to have a more balanced TSH, if one is monitoring their thyroid health or how they are responding to prescription thyroid medication, it is most important to gather readings that provide a full insight into how the thyroid is functioning at its most difficult/least balanced time of the day.  From this recent research, it is most importnat then to have the TSH measured in the morning.