What are the benefits and harms of thyroid hormones for adults with subclinical hypothyroidism (SCH)? This guideline was triggered by a recent systematic review of randomised controlled trials, which could alter practice. Current guidelines tend to recommend thyroid hormones for adults with thyroid stimulating hormone (TSH) levels >10 mIU/L and for people with lower TSH values who are young, symptomatic, or have specific indications for prescribing. The guideline panel issues a strong recommendation against thyroid hormones in adults with SCH (elevated TSH levels and normal free T4 (thyroxine) levels). It does not apply to women who are trying tobecome pregnant or patients with TSH >20 mIU/L. It may not apply to patients with severe symptoms or youngadults (such as those ≤30 years old).