Divergent Patterns of Thyrotropin and Other Thyroidal Parameters in Relationship with the Sex of Healthy Neonates and Infants Less than Two Years Old: A Longitudinal Study.

A longitudinal study was conducted in full-term healthy infants who were born between 2015 and 2017 in Athens, Greece, to elucidate the evolution of thyrotropin (TSH) and other thyroidal parameters according to sex, from their day of birth until two years old. Other thyroidal parameters that were taken into account include antithyroid peroxidase antibody (TPO-Ab) and antithyroglobulin antibody (TG-Ab), total triiodothyronine (T3), and free triiodothyronine (fT3), along with total thyroxine (T4) and free thyroxine (fT4). Blood samples were taken at 5-day intervals from the day of birth until the 31st day of life, and then every 5th month until 2 years of age.