When to treat mild hypothyroidism

Mild thyroid hormone deficiency, defined by elevation of serum thyroid-stimulating hormone concentration despite a normal free thyroxine level, can be distinguished by clinical and circumstantial observations from other conditions that cause this constellation of laboratory findings. In most but not all clinical trials, thyroxine treatments of patients with mild hypothyroidism have been shown to lower atherogenic lipid levels and relieve certain somatic and neuropsychiatric symptoms. Treatment also prevents progression to overt hypothyroidism, which is likely to occur in patients who are older, have circulating thyroid autoantibodies, or have a serum TSH level greater than 10 mU/L. The prevalence of mild hypothyroidism, particularly in older women, and its subtle clinical presentation have led some investigators to recommend a low threshold for case-finding or routine population screening for the disorder.