THYROXINE, THYROTROPIN, AND AGE IN A EUTHYROID HOSPITAL PATIENT POPULATION

The diagnosis of thyroid disease now often can be achieved reliably by measuring thyrotropin (TSH) alone. Thyroxine (T-4), triiodothyronine, and other analytes are only needed if TSH and the accompanying clinic al condition are discordant. We describe here work that confirms the a ge independence of TSH in both inpatient and outpatient euthyroid hosp ital populations between ages 20 and at least 80 years, and demonstrat es that although free T-4 does vary with age, the range of variation r emains within the T-4 reference interval. On this basis, TSH-based thy roid diagnostic algorithms can be used reliably in adults without refe rence to age-related reference intervals.