Objective: To determine the biochemical parameters of thyroid function in the cord blood of Saudi infants.
Methods: Cord blood samples sent to the Pathology Department for screening for congenital hypothyroidism were used to determine the reference ranges for thyrotropin, free thyroxine, free triiodothyronine, thyroxine-binding globulin and thyroglobulin. All the measurements were carried out by immunoassay (Elisa, microparticle enzyme immunoassay or chemiluminescence immunoassay). Reference ranges were calculated after exclusion of outliers.
Results: Reference ranges for thyrotropin, free thyroxine and thyroxine-binding globulin were similar to published values, whereas those for free triiodothyronine and thyroglobulin were different.
Conclusion: For correct interpretation of the parameters of thyroid function in cord blood it is essential to have reference ranges based on the laboratory's current methods and derived from the local population.