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March 23/30, 2005

Thyroid Status and Survival in Old Age—Reply

Author Affiliations

Letters Section Editor: Robert M. Golub, MD, Senior Editor.

JAMA. 2005;293(12):1447-1448. doi:10.1001/jama.293.12.1447-c

In Reply: Dr Scobbo addresses an important issue in clinical medicine: how to define normal reference values. The statistical method of determining reference ranges in a group of apparently healthy elderly patients is prone to bias because there is marked heterogeneity among elderly persons, it is difficult to distinguish between health and disease in this population, and disability that is not formally classified as disease is common. In contrast to a parameter such as hemoglobin levels for which we believe the normal range should not be adjusted in an older population,1 our present analyses of thyroid hormone levels indicate that the normal values of thyrotropin and free thyroxine may need to be redefined in the oldest old population.

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