Samuels MH, et al. - Given that the brain is a critical target organ for thyroid hormone, researchers investigated whether variations in thyroid function within and near the reference range affect the quality of life, mood, or cognition. For this analysis, 138 patients with levothyroxine (L-T4)-treated hypothyroidism and normal thyrotropin (TSH) levels underwent measures of quality of life (36-Item Short Form Health Survey, Underactive Thyroid-Dependent Quality of Life Questionnaire), mood (Profile of Mood States, Affective Lability Scale), and cognition (executive function, memory). They found that altering L-T4 doses in hypothyroid patients to vary TSH levels in and near the reference range did not affect the quality of life, mood, or cognition. Despite a lack of objective benefit, L-T4-treated subjects prefer perceived higher L-T4 doses. Findings suggested that adjusting L-T4 doses in hypothyroid patients based on symptoms in these areas could not result in significant clinical improvement.