Thyroglobulin Reference Values in a Pediatric Infant Population
Few reports have addressed normal serum thyroglobulin (Tg) values in newborns and infants. In the present study, serum Tg was measured in 228 normal children (110 females and 118 males) aged from 3 to 180 days of life, all presenting normal age-related serum thyrotropin (thyroid-stimulating hormone [TSH]) values and negative anti-Tg and antithyroperoxidase antibodies. Serum Tg was measured by Radioimmunoassay (RIA) (two methods) and Immunometricassay (IMA) (three methods). Mean Tg values measured by the five methods exhibited among-method biases, although a significant positive correlation was observed. Serum Tg levels measured by the five methods showed a correlation with age, but not with TSH or gender. During the first days of life, relatively high mean Tg levels were observed, which progressively decreased until they reached a plateau. Therefore, with the aim of establishing reference values, the population was separated into two age groups: from 3 to 15 days of life (group A) and from 16 to 180 days ...