Subclinical hypothyroidism

Subclinical hypothyroidism is defined as elevated serum thyroid stimulating hormone (TSH) while normal free T4 (FT4) levels. The etiology of subclinical hypothyroidism is the same as that of overt hypothyroidism. Patients with subclinical hypothyroidism may be asymptomatic or have only mild non-specific symptoms. The diagnosis is based on laboratory results but other causes of TSH elevation such as recovery form nonthryoid illness or adrenal insufficiency should be rule-out before making the diagnosis. Repeating the laboratory tests may be necessary to confirm the diagnosis. Treatment with thyroxine may be considered in those who has TSH level higher than 10 IU/mL, or has elevated TSH level but lower than 10 IU/mL and anti-thyroid peroxidase antibody positive. In pregnant women with subclinical hypothyroidism, thyroxine supplement is recommended. Thyroid function tests may be considered in women with risk factors for subclinical hypothyroidism when pregnant or pregnancy is intended.