Levothyroxine is also used to treat subclinical hypothyroidism, which is defined by an elevated TSH level and a normal-range free T4 level without symptoms. Such people may be asymptomatic and whether they should be treated is controversial. One benefit of treating this population with levothyroxine therapy is preventing development of hypothyroidism. As such, treatment should be taken into account for patients with initial TSH levels above 10 mIU/l, people with elevated thyroid peroxidase antibody titers, people with symptoms of hypothyroidism and TSH levels of 5–10 mIU/l, and women who are pregnant or want to become pregnant. Oral dosing for patients with subclinical hypothyroidism is 1 μg/kg/day.