The guideline, published in the BMJ, was triggered by a systematic review of randomised controlled trials which showed that hormone treatment did not improve quality of life or symptoms in patients with subclinical hypothyroidism.
In light of this finding, the guideline panel of clinicians, methodologists and patients recommended against routinely prescribing thyroid hormones in adults with elevated TSH levels and normal free T4 (thyroxine) levels.
However, in a joint statement published on 29th May, the Society for Endocrinology and the British Thyroid Association rejected the panel's recommendation. The bodies expressed concern that patients with subclinical hypothyroidism could miss out on vital treatment if their condition progresses, as a result of the panel's 'over-extrapolation of data, most of which is from older patients with milder symptoms or from small-scale studies'.
Current guidelines generally recommend thyroid hormones for adults with TSH levels >10mIU/L and for people with lower TSH values who are young, symptomatic, or have specific indications for prescribing. Research shows that the prevalence of hormone treatment for subclinical hypothyroidism doubled in the decade between 1996 and 2006.
The systematic review that informed the BMJ guideline included 21 trials with 2192 participants. The reviewers concluded that thyroid hormones consistently demonstrated no clinically relevant benefits on quality of life or thyroid-related symptoms (including depression, fatigue, and BMI) in patients with subclinical hypothyroidism. Lower-quality evidence suggested that thyroid hormones may have little or no effect on cardiovascular events or mortality.
The panel's recommendation does not apply to women who are trying to become pregnant or patients with TSH >20 mIU/L. It may not apply to patients with severe symptoms or young adults (such as those ≤30 years old).