As many as 13 million Americans may have an undiagnosed thyroid problem, according to a study known as the Colorado Thyroid Disease Prevalence Study. The study was performed by Knoll Parmaceutical (makers of Synthroid). Over 25,000 participants were studied in 1995. The researchers found that nearly 9% of the participants who were not on thyroid medication were hypothyroid and a little over 1% were hyperthyroid. If this number were extrapolated to the entire US population, the number of patients with an undiagnosed thyroid problem would number 13 million. The study also found that even “subclinical” hypothyroidism, may raise cholesterol levels.

Research appearing in the American Journal of Psychiatry (March 1993;150:3:508-510) suggests that the thyroid may be involved with some cases of depression. It was a small study that looked at 16 patients with subclinical hypothyroidism and 15 with normal thyroid function. The frequency of depression over the course of a lifetime was higher in the group with subclinical hypothyroidism.