Do not treat subclinical hypothyroidism!

Adults with subclinical hypothyroidism should not be treated with thyroid hormones, according to a new guideline from The BMJ's Rapid Recommendations panel.

The recommendation, characterised as "strong," applies to those with elevated thyroid-stimulating hormone levels (but still below 20 mIU/L) plus normal thyroxine levels noted on two or more consecutive tests. Patients may or may not have mild-to-moderate symptoms.

The recommendation was driven by data from a 2018 meta-analysis, plus a large 2017 trial of treatment in elders. The panel concluded that there are "no important benefits from treatment," while the possibility of treatment harms — including a potentially higher mortality risk — could not be excluded.

The guideline does not apply to women who are attempting a pregnancy. Additionally, it may not apply to those with severe symptoms or adults aged 30 and younger.