A recent study known as the Colorado Thyroid Disease Prevalence Study, found that 13 million Americans may have undiagnosed thyroid conditions, and suggested that more widespread thyroid testing is needed. Among their findings are the fact that 9.9 percent of the population had a thyroid abnormality that had gone unrecognized. An underactive thyroid -- hypothyroidism -- affects more women than men, and the risk increases with age for both men and women. Clearly, there is a need for more widespread thyroid stimulating hormone (TSH) testing and more aggressive treatment, especially for subclinical patients. Additionally, another study, called the NHANES study, showed that the reference ranges (for TSH) in most laboratories are too wide. Furthermore, relying on the TSH (being in the normal range) as the only way to define hypothyroidism may mean that still more millions are hypothyroid, but undiagnosed and overlooked.
A thorough workup of the thyroid axis should include an assessment of the adrenal axis as well. Of course a history (dry skin, hair loss, constipation, weight gain, brittle nails, irregular menses, muscle weakness, sensitivity to cold, recurrent upper respiratory tract infections, depression, low energy, hoarseness, elevated cholesterol), physical exam, body temperatures, and lab testing (TSH, free T4 , Free T3, reverse T3) are part of a complete evaluation.
Finally, another new study (of 17, 684 people) showed that when one is on thyroid hormone, an optimal dose is one that keeps the TSH very low, but not completely suppressed. This reduces risks of cardiovascular complications and fractures. These results are surprising, but the study was quite strong in design. (J. Clin Endocrinology Metab, Jan 2010, 951(1):185-193).