An early form of underactive thyroid (when the body doesn't produce enough thyroid hormones) called subclinical hypothyroidism is a common condition but the benefit of thyroid hormone therapy on quality of life and symptoms is uncertain. This study, which analyzed the combined results of 21 randomized clinical trials with 2,200 participants with subclinical hypothyroidism, reports that thyroid hormone therapy wasn't associated with improved quality of life or thyroid-related symptoms.