Thyroid hormones should not be routinely offered to adults with a mildly underactive thyroid gland – known as subclinical hypothyroidism – a panel of international experts has warned.
Their recommendation, published in the British Medical Journal, was based on new evidence that it does not improve quality of life or symptoms including low mood and fatigue.
“For adults with SCH, thyroid hormones consistently demonstrate no clinically relevant benefits”
Subclinical hypothyroidism (SCH), detected by a blood test, occurs when the thyroid stimulating hormone (TSH) levels in the bloodstream are slightly raised, while the level of thyroid hormone remains normal.
It affects up to 5% of the adult population, but 10-15% of older people. While some have no symptoms, others can show mild signs of fatigue, low mood and weight gain.
About 25% of UK adults have thyroid function tests every year and guidelines tend to recommend hormones for those with TSH levels above 10 mIU/L – a normal TSH level is 0.4 to 4.0 mIU/L.
The authors of the new article highlighted that research showed that hormone treatment for SCH had doubled from 1996 to 2006.
As a result, they developed guidance using a recent a systematic review of 21 trials and about 2,200 patients comparing thyroid hormone treatment with no treatment or placebo in adults with SCH.
The panel made a “strong” recommendation against thyroid hormones for almost all adults with SCH, because there were no benefits from treatment on fatigue, low mood, weight gain or any other outcomes that were tested.
In addition, they noted that taking a pill and attending lifelong check-ups was burdensome and they could not rule out the possibility of associated harms.
While they did not take costs and resources into account beyond direct costs to patients, they also warned that thyroid hormones could not be cost effective.
The recommendation does not apply to women who are trying to become pregnant or patients with particularly high TSH levels – above 20 mIU/L.
It may also not apply to patients with severe symptoms or some aged under 30, they noted.
They stated: “For adults with SCH, thyroid hormones consistently demonstrate no clinically relevant benefits for quality of life or thyroid related symptoms, including depressive symptoms, fatigue, and body mass index (moderate to high quality evidence).
“Thyroid hormones may have little or no effect on cardiovascular events or mortality (low quality evidence), but harms were measured in only one trial with few events at two years’ follow-up,” they added.
They called for future research to explore whether there was an unidentified group of patients who might benefit from treatment.
However, in the meantime, they said their recommendation, if introduction, “may substantially alter prescribing trends”.