brand logo

Am Fam Physician. 2014;90(2):114

Clinical Question

How much do seemingly stable thyroid tests vary over time?

Bottom Line

Most patients receiving thyroid replacement therapy with less than 125 mcg of levothyroxine per day can wait two years before monitoring thyroid-stimulating hormone (TSH) levels if their results are normal. Fewer than one in 10 patients who take less than 125 mcg of levothyroxine per day with a normal TSH level will have an abnormal laboratory value one year later. The likelihood goes up to 26.7% if the dosage is higher than 125 mcg of levothyroxine per day. Patients with TSH levels closer to the upper or lower limits of normal will also be slightly more likely to have an abnormal value in one year. (Level of Evidence = 1b)

Synopsis

These authors identified 715 patients (84% women; average age = 54 years) in a single primary care practice who were treated for hypothyroidism and had a normal TSH value (0.3 to 5.0 mIU per L). They recorded all subsequent TSH levels in these patients for the following six years. Age, sex, body mass index, and history of chronic autoimmune thyroiditis were not associated with the development of a subsequent abnormal TSH level, but the dosage of levothyroxine was associated. Approximately one in four patients taking more than 125 mcg of levothyroxine per day (26.7%) had an abnormal TSH level one year later. Most of the patients taking lower dosages (91.1%) had normal TSH levels one year later.

Study design: Cohort (retrospective)

Funding source: Self-funded or unfunded

Setting: Outpatient (primary care)

Reference: PecinaJGarrisonGMBernardMELevothyroxine dosage is associated with stability of thyroid-stimulating hormone values. Am J Med.2014; 127( 3): 240– 245.

POEMs (patient-oriented evidence that matters) are provided by Essential Evidence Plus, a point-of-care clinical decision support system published by Wiley-Blackwell. For more information, see http://www.essentialevidenceplus.com. Copyright Wiley-Blackwell. Used with permission.

For definitions of levels of evidence used in POEMs, see https://www.essentialevidenceplus.com/Home/Loe?show=Sort.

To subscribe to a free podcast of these and other POEMs that appear in AFP, search in iTunes for “POEM of the Week” or go to http://goo.gl/3niWXb.

This series is coordinated by Natasha J. Pyzocha, DO, contributing editor.

A collection of POEMs published in AFP is available at https://www.aafp.org/afp/poems.

Continue Reading


More in AFP

More in PubMed

Copyright © 2014 by the American Academy of Family Physicians.

This content is owned by the AAFP. A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. This material may not otherwise be downloaded, copied, printed, stored, transmitted or reproduced in any medium, whether now known or later invented, except as authorized in writing by the AAFP.  See permissions for copyright questions and/or permission requests.