TSH ACCORDING TO AGE AND SEX, DECREASES THE PRESUMPTIVE DIAGNOSIS OF HYPOTHYROIDISM

Introduction: The reference ranges for classifying a patient as hyperthyroid, normothyroid or
hypothyroid vary from one laboratory to another, due to the different techniques used, regional
factors, such as race, iodine intake, etc. But there are also other variables, like the age and the sex of
the patient that generally are not taken into account, but can play a role in the diagnosis.
Objectives: To apply the formulas from the NHANES III study, to a Madrid (Spanish) population.
Patients and methods: We included 2521 patients: they were requested TSH and thyroid antibodies
(antimicrosomial thyroid antibodies and thyroglobulin) by their family physicians. The TSH, T3 and
T4 tests were also requested.
Results: Of 181 patients (134 women and 47 men), corresponding to 12% of the total and 63.7 % of
patients classified as hypothyroid, which were reclassified as normothyroid. Only 2 patients (100 %
men), corresponding to 0.08% of the total and 0.20% of patients initially classified as normothyroid,
were reclassified to hyperthyroid.
Discussion: The results of our study show a significant decrease in patients classified initially as
hypothyroid and then reclassified as normothyroid depending on their age and sex. All these
equations could be programmed into the laboratory´s computer system and would not need further
testing.
Conclusions: Classification errors would be reduced in patients with TSH below the 2.5 percentile or
above the 97.5 percentile of its reference range of TSH.