Aproximación al patrón de normalidad de TSH para la población chilena según Encuesta Nacional de Salud 2009-2010 Thyroid stimulating hormone reference values derived from the 2009-2010 Chilean National Health Survey

Background: The determination ofthyroid stimulating hormone (TSH) reference values is critical for the diagnosis ofthyroid diseases. Aim: To explore and discuss different definitions to establish TSH reference values using a Chilean national survey sample. Material and Methods: The 2009-2010 Chilean National Health Survey recruited 5,416participants between the ages of 15 and 96years, from all geographic regions of Chile, including urban and rural zones. TSH was measured in a random subsample of 2,785 adults. Median value, 2.5 and 97.5 percentiles were described in three different populations: total survey population, "disease-free population" and the "laboratory kit disease free population". Results: TSH values were higher among women, the elderly and the less educated population. The 97.5 percentile value in the disease-free population was 7.46 uUl/ml. Using this value as a cut-off, hypothyroidism prevalence would be 4.8% in Chile and estimated pharmacological treatment coverage would be 58%. When laboratory kit cut-offs are used, prevalence rises to 22% and treatment coverage drops to 12%. The 2.5 percentile value in the disease-free population was 0.83 uUl/ml, which yields an estimated hyperthyroidism prevalence of3.89%. Conclusions: Median TSH concentration values in the Chilean "disease-free population" are higher than those proposed by laboratory kits and those of developed countries. TSH values in the general population of Chile are also higher in women, the elderly and the less educated population.