Endocrine Society
View all recommendations from this societyReleased October 16, 2013*; updated July 17, 2017
Don’t order a total or free T3 level when assessing levothyroxine (T4) dose in hypothyroid patients.
T4 is converted into T3 at the cellular level in virtually all organs. Intracellular T3 levels regulate pituitary secretion and blood levels of TSH, as well as the effects of thyroid hormone in multiple organs. However, T3 levels in blood are not reliable indicators of intracellular T3 concentration. Compared to patients with intact thyroid glands, patients taking T4 may have higher blood T4 and lower blood T3 levels. There is controversy as to whether a normal TSH reflects adequate intracellular T3 levels in all organs, However, even in patients taking both levothyroxine and liothyronine, there are no data suggesting that the blood level of total or free T3 correlates with a patient’s clinical response. Therefore, in most patients a normal TSH indicates a correct dose of T4.
These items are provided solely for informational purposes and are not intended as a substitute for consultation with a medical professional. Patients with any specific questions about the items on this list or their individual situation should consult their physician.
How The List Was Created
Members of the Endocrine Society (Society) along with representatives of the American Association of Clinical Endocrinologists (AACE)* formed a joint task force to identify tests or procedures which should only be used in specific circumstances. The task force identified several items for possible inclusion. Subsequent discussions compared the evidence supporting each item, the value of the recommendation to practitioners and the potential for cost savings. Members of the Society’s Clinical Affairs Core Committee and AACE leadership also reviewed the initial list. Using the above criteria, the task force voted for their top five recommendations from the original list. The Society’s Council and AACE’s Board of Directors approved the final list for submission to the Choosing Wisely® campaign.
The Endocrine Society disclosure and conflict of interest policies can be found at www.endocrine.org.
*The American Association of Clinical Endocrinologists withdrew from the Choosing Wisely campaign on May 26, 2015.
Sources
Garber JR, Cobin RH, Gharib H, Hennessey JV, Klein I, Mechanick JI, Pessah-Pollack R, Singer PA, Woeber KA. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012; Sep 11:1–207.
