New clinical practice guidelines strongly recommend against the routine use of thyroid hormones in adults with subclinical hypothyroidism, based on a systematic review published in the BMJ.

Subclinical hypothyroidism is defined biochemically as elevated levels of thyroid-stimulating hormone with normal free thyroxine levels. Patients in this state can be asymptomatic or have nonspecific symptoms. Although there is inconclusive evidence regarding the benefit of screening for subclinical hypothyroidism, some guidelines have recommended screening of adults every 5 years to identify thyroid disorders.

In a systematic review for this clinical practice guideline, the researchers compared the effects of thyroid hormone with placebo or with no treatment in adults with subclinical hypothyroidism. Of the 21 studies (2192 participants) included in the systematic review, results of the TRUST trial dominated the outcomes.

An international panel included methodologists, general practitioners, internists, endocrinologists, and patient partners with subclinical hypothyroidism. The panel provided a strong recommendation stating that thyroid hormones should not be routinely offered to adults with subclinical hypothyroidism, as they do not lead to important benefits in quality of life or thyroid-related symptoms in this population. Furthermore, the option to treat may be more burdensome for patients, as treatment requires daily medication that may be required for a long period of time, in addition to follow-up and blood tests for thyroid function tests and dose adjustments.

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Although the experts did not take costs and resources into account, the evidence that thyroid hormones have no important benefit and the potential for harm and associated costs in this population supports that this treatment cannot be cost-effective.

The panel concluded that most adults with subclinical hypothyroidism would not benefit from thyroid hormone treatment. However, these recommendations do not apply to women who are trying to become pregnant, young adults (age ≤30 years), or patients with significantly elevated thyroid-stimulating hormone or severe symptoms.

As the data indicate the prevalence of treated subclinical hypothyroidism doubled between 1996 and 2006, the experts believe that if this guideline is implemented, a significant effect on the prescribing trends for thyroid hormones should be expected.

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Reference

Bekkering GE, Agoritsas T, Lytvyn L, et al. Thyroid hormones treatment for subclinical hypothyroidism: a clinical practice guideline. BMJ. 2019;365:l2006.