Changes in thyroid function with age: results from the Pizarra population-based longitudinal study

Summary Background Results of studies examining the influence of age on thyroid function and TSH levels, in the absence of thyroid disease, remain controversial. The aim of this study was to determine the course of thyroid function over 11 years in a population with normal thyroid function. Methods This is a population‐based prospective study started in 1995–1997 (first phase), and reassessed 6 (second phase) and 11 years later (third phase). Results The TSH and FT4 in the third phase were significantly increased (p = 0.001 and p = 0.001, respectively), with the values being higher particularly from the age of 50 years. In those persons with a baseline TSH ≥ 1.2 and