Often overlooked, optimization of thyroid hormone levels can play a significant role in well-being and healthy aging. For those with hypothyroidism (overt or subclinical), we manage the thyroid by paying attention to free T3 levels as well as the usual TSH and T4. Low levels of Free T3 are a commonly-overlooked condition that may result in symptoms of hypothyroidism including fatigue, chronically feeling cold, chronic constipation, and hair loss.