Longitudinal Changes in thyroid function and TSH bioactivity in older participants from the Whickham cohort – implications for diagnosis of hypothyroidism
Dr Salman Razvi, Senior Lecturer and Consultant Endocrinologist, Newcastle University and Professor Marian Ludgate, Professor of Molecular Endocrinology, Cardiff University
An under-active thyroid, diagnosed when blood thyroid hormones are low and the pituitary thyroid stimulating hormone (TSH) is elevated, is more common in older individuals and in women. Mild forms of underactive thyroid are increasingly being diagnosed when blood TSH levels are high but thyroid hormones are within the normal range. But, TSH levels increase in older people (> 70 years) and are not always associated with any harmful effects on health. Moreover, the TSH normal range has been obtained from mainly younger people and may therefore not be suitable to diagnose thyroid disease in older individuals. In addition, it is unclear why TSH levels increase with age and what the underlying mechanism is. This project intends to study a group of 200 carefully selected individuals without thyroid disease that have had their full thyroid function measured a few years ago (in 2007 – 10) with a more recent thyroid function measurement. This will provide us with information on changes in TSH levels over time in the same person along with any effect on thyroid hormone concentrations. The impact of other important factors such as gender, smoking and blood markers of immune-activity against the thyroid will also be assessed. Finally, in a smaller sub-group of 50 people from the main study, laboratory tests will study if the stimulatory action of TSH changes with age. The results of this project will increase our understanding of the changes in thyroid function with age, and will enhance the debate on using age-appropriate reference ranges to assess thyroid function. This could ultimately lead to better and more suitable management of under-active thyroid disease in older people.