As people age their requirement for thyroid hormone replacement might decrease because there is a natural reduction of thyroid hormone production, secretion, and degradation with the years. People taking levothyroxine, therefore, may require periodic dose reductions.
This is important because overtreatment with levothyroxine can have adverse effects such as increased heart rate and an increase in the risk for atrial fibrillation.
Also, hyperthyroidism itself is known to be associated with decreased bone quality and bone mineral density.
To prevent overtreatment and its potention risk have a TSH test at least once per year and be watchful for the signs and symptoms of hyperthyroidism (increased heart rate, heat intolerance, weight loss, irritability, fatigue and difficulty sleeping).
Unless otherwise ordered by your physician it is usually best to take your thyroid replacement in the morning at least 30 minutes before breakfast for the best absorption. It is equally important to be consistent whenever you take it.