Subclinical hypothyroidism is defined as elevated thyroid stimulating hormone (TSH) and a serum free thyroxine level (free T4) within the reference range. Most patients with subclinical hypothyroidism have no symptoms or have nonspecific symptoms.
About 18% of adults 65 years of age or older have characterises of subclinical hypothyroidism. Subclinical hypothyroidism is a possible contributor to many problems in older persons: vascular system and the heart, the brain, skeletal muscle, and bone.
Recent study examined whether there are clinical benefits from Thyroid Hormone Therapy in older persons with subclinical hypothyroidism. Following recent guidelines for older persons a TSH target was set of 0.40 to 4.60 mIU per liter with levothyroxine treatment. The results show that treatment with levothyroxine in older persons with subclinical hypothyroidism provided no symptomatic benefits.
Though this study did not measure thyroid antibody levels. Patients with thyroid antibodies (TPO, TgAb) are more likely to have progressive hypothyroidism and therefore may be more likely to have a benefit from long-term levothyroxine treatment. Thus the possibility that treatment with levothyroxine may provide cardiovascular protection or cause harm cannot be excluded.