Thyroid function tests in sick euthyroid elderly patients: A longitudinal study

Cross-sectional studies have shown that thyroid function tests are often deranged in elderly patients with non-thyroidal illness. The behaviour of thyroid function tests over time was studied in 31 sick elderly patients in the hope of identifying the most appropriate thyroid function test(s) as well as the optimum time for their implementation. We found that 82% of patients had depressed serum free triiodothyronine (FT3) levels within 24 hours of hospitalisation. In addition, serum thyrotropin (TSH) was often abnormal, though this was first noted at any time from day 1 to day 20. However, serum free thyroxine (FT4) was not deranged in any patient until after day 3, suggesting that there might be an exploitable time lag from the onset of acute illness to the development of an abnormal FT4.