Towards operationally defined reference values for thyroid function tests
01 / 2005 - unknown
Although thyroid diseases affect subjects of all ages, both hyper- and hypothyroidism are prevalent among elderly people. Graves? hyperthyroidism as the commonest cause of hyperthyroidism has its second incidence peak at 60-69 years of age. The second leading cause of thyrotoxicosis, toxic multinodular goiter, affects predominantly elderly people with an age of Although thyroid diseases affect subjects of all ages, both hyper- and hypothyroidism are especially prevalent among elderly people. Graves? hyperthyroidism as the commonest cause of hyperthyroidism has its second incidence peak at 60-69 years of age.(1,2) The second leading cause of thyrotoxicosis, toxic multinodular goiter, affects predominantly elderly people with an age of In this project we want to develop operationally defined reference values for TSH in the elderly population by relating certain TSH levels with the risk for thyroid disease associated adverse health outcomes. We will do this by relating TSH levels at base line during the ERGO 1 visit with subsequent (incident) outcomes during 10-12 years of follow-up (at ERGO 2-4 visits). TSH levels will thus be related to the relative Risk for the development of the following outcomes: For hyperthyroidism: 1) Atrial fibrillation; 2) Cardiavascular mortality and cardiac disorders such as increased left ventricle mass and diastolic dysfunction; 3) osteoporotic fractures, and bone density; 4) Alzheimer?s disease; 5) progression towards overt hyperthyroidism. Several highly relevant chronic diseases of the elderly are related to thyroid dysfunction. Atrial fibrillation (and its complication stroke), as well as osteoporosis are established consequences of overt hyperthyroidism. There is accumulating but insufficient evidence that subclinical hyperthyroidism is also associated with atrial fibrillation, at least for TSH levels TSH concentrations and TPO autoantibody titers have been determined in a random selection of 2,000 subjects included in the ERGO 1 cohort of 7,983 participants aged 55 years and older from the Rotterdam suburb Ommoord, who were included in 1990-1993. (11) To amass a larger study group, we will also determine TSH and anti-TPO antibody levels in all samples that are still available from the 6,513 participants investigated in the ERGO 2 visit. All these subjects have been subsequently investigated thoroughly at three (or two) moments in time (ERGO 2-4) and this enables us to relate their base-line TSH values to several thyroid-associated adverse health outcomes that have occurred during follow-up. The impact of overt hyper- and hypothyroidism in the elderly is well known, but whether subclinical hyper- or hypothyroidism is also associated with a number of adverse health outcomes (see below) is uncertain.