performance, and an overall decrease in their quality of life. Patients with unrecognized hyperthyroidism are at risk for myocardial infarction, serious cardiac arrhythmias, including atrial fibrillation, anxiety, muscle weakness, diminished productivity, and decreased quality of life.
We're particularly concerned about the importance of TSH measurements in evaluating the effectiveness of thyroxine therapy in patients with thyroid cancer. We must be sure that TSH is fully suppressed to minimize the likelihood of growth and spread of residual tumor throughout the life of these patients. A decrease in thyroxine as small as 12 micrograms can cause dangerous TSH elevations in a formerly suppressed patient. TSH monitoring is also critical since changes in TSH levels can occur due to medications, like iron, amiodarone, Zoloft, and lithium. Patients and even some physicians may not be aware of the potential thyroid effects of some of these drugs.
The FDA has recommended evaluation of thyroid hormone bioequivalence by giving 600 micrograms of thyroxine to healthy volunteers and studying its