CCL Featured Stories, Homepage Featured Stories, Recommendations from the Choosing Wisely® Initiative
Choosing Wisely®: Thyroid Function Testing
Thyroid function disorders are relatively common in the population, affecting up to 5-10% of the U.S. population. Since clinical symptoms are variable and non-specific, laboratory testing is generally used in diagnosis.
Thyroid-stimulating hormone (TSH) is produced by the pituitary gland and helps signal the thyroid gland to produce more or less thyroxine (T4) and triiodothyronine (T3). TSH is sensitive in detecting subclinical thyroid dysfunction and is therefore the primary screening test for thyroid disease.
If the TSH level is normal, additional testing is generally not indicated. If TSH is high, hypothyroidism should be suspected and can be further investigated and confirmed by testing free T4 levels. If TSH is low, hyperthyroidism can be detected by again testing for free T4 and if required T3 levels. In such cases, T3 levels should be done when Free T4 is normal and there is clinical suspicion for hyperthyroidism.
Dr. Ansari from Cleveland Clinic’s immunopathology laboratory reminds providers: “…only 0.03 % of T4 is physiologically active free hormone – 99.97% is bound to serum proteins – thus, measuring total T4 may not be useful clinically.”
- Don’t order multiple tests in the initial evaluation of a patient with suspected thyroid disease. Order thyroid-stimulating hormone (TSH), and if abnormal, follow up with additional evaluation or treatment depending on the findings. (1)
- Don’t order a total or free T3 level when assessing levothyroxine (T4) dose in hypothyroid patients, as treatment itself may impact T3 levels. (2)
- Don’t routinely order a thyroid ultrasound in patients with abnormal thyroid function tests if there is no palpable abnormality of the thyroid gland. (2)
Choosing Wisely® Initiative of the American Board of Internal Medicine:
1. American Society for Clinical Pathology
2. Endocrine Society
- LeFevre ML, U.S. Preventive Services Task Force. Screening for thyroid dysfunction: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2015 May 5;162(9):641-50.
- Jonklaas J, Bianco AC, Bauer AJ, et al. on behalf of the American Thyroid Association Task Force on Thyroid Hormone Replacement. Guidelines for the treatment of hypothyroidism. Thyroid. 2014;24(12):1670-1751.
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