The distribution of TSH values in the population differs by age. In an analysis of 16,533 individuals in the National Health and Nutrition Examination Survey III (NHANES III), there was an age-related shift toward higher TSH concentrations in older patients. For example, the 97.5 centile for TSH in adults aged 20 to 29 years, or over age 80, was 3.56 and 7.49 mU/L, respectively. Seventy percent of the individuals in the older group with a TSH greater than 4.5 mU/L were within the normal range for their age.
Higher TSH levels in the elderly may be associated with health benefits rather than health problems, and controversy exists as to whether patients with serum TSH values between 5 and 10 mU/L require treatment.
