How is thyroid hormone replacement therapy monitored?
Patients who are treated with thyroid hormone replacement therapy are usually monitored with serial measurements of TSH levels. This approach to monitoring is based on idea that the amount of TSH secreted by the pituitary gland provides the most sensitive indication of whether there is an adequate amount of thyroid hormone present in the body. Individual therapy is usually targeted to identify a daily dose of levothyroxine that will supplement any T4 and T3 produced by remaining thyroid tissue to provide an adequate amount of thyroid hormone. Successful treatment is usually indicated by the measurement of TSH levels that fall within the limits of the reference range. The reference range for TSH is usually stated to be 0.5-5.0 mU/ml (microunits per milliliter), though there may be slight variation from laboratory to laboratory. TSH levels that fall above the upper limit of the reference range may indicate that there is not enough thyroid hormone present in the body. This may signal the
