Reference Intervals for Thyrotropin Hormone in the General Andean Population of Quito-Ecuador Using...

Thyroid function is one of the most current procedures in the evaluation of endocrine function performed in daily practice; the reference intervals for thyrotropin (TSH) depend on the assay technology and the instruments in each laboratory. The main objective of this study is to determine the thyrotropin reference values in patients considered as euthyroid, living in the Andean region, at 2850 meters above sea level (Quito, Ecuador).

A cross-sectional, analytical, epidemiological study was conducted using a sample of 595 healthy adult volunteer donors from the Military Hospital Blood Bank in Quito-Ecuador. Serum samples were analyzed for thyrotropin levels using electrochemiluminescence. The reference values were calculated using recommendations from the CLSI C28A3 guide.

The mean age of the overall sample was 35.7 (7.2) years, 50.9% (n = 303) were women. TSH recovered in the total sample showed a median of 2.64 mIU/L (2.5th-97.5th percentiles: 0.91-8.35 mIU/L); after removing outliers the reference values for the studied population were 0.87 to 5.21 mIU/L, without differences by sex.

General laboratory practice should improve harmonization of TSH assays. This is a must in daily clinical practice, since it would allow us to share real reference intervals in an established population and may be related to the presence or absence of thyroid pathology.