By Bianca Nogrady
Thyroid hormone therapy does not appear to offer any benefits for quality of life or thyroid-related symptoms in adults with subclinical hypothyroidism, according to a systematic review and meta-analysis published in JAMA.
An international team of researchers reviewed and analysed 21 randomised clinical trials of thyroid hormone therapy in a total of 2192 nonpregnant adults with a thyrotropin level above the reference range and a free thyroxine level within the reference range.
The researchers found that while thyroid hormone therapy with triiodothyronine, thyroxine or both achieved normalisation of mean thyrotropin compared with placebo, there were no significant benefits for quality of life or thyroid-related symptoms.
For secondary outcomes, they found no benefit of thyroid hormone therapy for depressive symptoms, fatigue, cognitive function, muscle strength, blood pressure or body mass index.
‘Although current guidelines are at first sight cautious with treatment recommendations, more than 90% of persons with subclinical hypothyroidism and a thyrotropin level of less than 10 mIU/L would actually qualify for treatment,’ the authors wrote.
The overall risk of bias was judged to be low and the quality of evidence assessed as moderate to high. However, the authors noted that the quality of evidence for any effect on cardiovascular disease (CVD) risk was low.
Commenting on the study, endocrinologist Professor John Walsh said the meta-analysis was dominated by a single large study of thyroxine treatment in older, asymptomatic people with minimally elevated thyroid stimulating hormone (TSH; thyrotropin) levels.
‘The findings are helpful in the management of older people with incidentally discovered high TSH levels, who can be safely left untreated,’ said Professor Walsh, from the University of Western Australia and Sir Charles Gairdner Hospital, Perth.
However, he stressed that the findings did not necessarily apply to younger patients, or those presenting with symptomatic subclinical hypothyroidism, as evidence in these groups was still lacking.
On the question of any impact on CVD risk, Professor Walsh said while observational study evidence pointed to subclinical hypothyroidism being a CVD risk factor, there were no randomised controlled trials showing thyroxine prevented CVD events.
JAMA 2018; 320: 1349-1359.