Reference Intervals from Birth to Adulthood for Serum Thyroxine (T4), Triiodothyronine (T3), free T3, free T4, Thyroxine Binding Globulin (TBG) and Thyrotropin (TSH)

Abstract

Disorders in thyroid function can impair normal development in children. Therefore it was our aim to establish reference intervals for serum triiodothyronine (T3), free T3 (fT3), thyroxine (T4), free T4 (fT4), thyroxine binding globulin (TBG) and thyrotropin (TSH) which are applicable from birth to adulthood by using the non-isotopic automated chemiluminescence immunoassay system, Immulite (DPC Los Angeles, USA). Serum samples from 762 euthyroid newborns, children and adolescents (369 female, 393 male; age 1 day to 19 years) were examined; of these, 381 were classified as pubertal. Due to non-normal distribution, the 2.5th, 50th and 97.5th percentiles (the central 95% interval) were calculated for each group. The median concentrations of T4, fT4 and TSH were up to 3.2-fold higher during the first 2 weeks, while T4 increased during the first month of life. The concentrations in all age groups showed no sex differences. From 1 year onwards, the concentration of all parameters tended to decrease until adult age, with the exception of TBG which increased by >60% (p<0.02) and reached a maximum at approximately 5 years of age. The findings underscore the fact that thyroid hormones are not associated with sexual development, except for TBG, which decreased slightly (p<0.04) between Tanner stages 1 and 5. However, the reference intervals established here demonstrate that marked changes occur in concentrations of thyroid hormones after the neonatal period. Our findings complement these of earlier studies. The developed reference intervals can be used to assess the thyroid status of patients, particularly if the measurements are done on the Immulite/Immulite 2000 system.

Pediatric reference intervals for FSH, LH, estradiol, T3, free T3, cortisol, and growth hormone on the DPC IMMULITE 1000

“…Our findings for LH, FSH, TT3, and FT3 agree with earlier studies on the Abbott IMx [11]. The data of Elmlinger utilized n values varying from 8 to 131 in the various age groups with many groups having an n<30 [12,13]. Despite this deficiency the data are similar to those in this manuscript which utilizes n values falling between n=45 and n=289.…”

Management of neonates born to women with Graves' disease: a cohort study

“…The FT 4 increase and TSH decrease developed gradually, after day 3 but before day 15 in neonates who subsequently developed hyperthyroidism. (Table 1) are consistent with the previously described time-course of FT 4 , FT 3 , and TSH values in neonates, once gestational age at birth is taken into account (25,36,37). When interpreting thyroid function data in neonates, the values must be compared with age-specific normal ranges.…”

Thyrotropin Levels Are Associated with Cardiometabolic Risk Factors in Euthyroid Adolescents

“…An intensive inpatient two-month weight-loss program for children and adolescents indicated that the change in TSH with weight loss predicted reductions in HOMA-IR after controlling for change in body weight, age, and sex, while the changes in fT3 and fT4 did not (37). Sex-related differences were observed in TSH, fT3 levels, and the fT3:fT4 ratios in this NHANES adolescent cohort, but since data on sexual maturity rating (Tanner Staging) were not recorded, it was not possible to assess the impact of pubertal progression on thyroid hormone levels directly, for which studies are conflicting (38,39). The variability in these results highlights the need for further prospective studies elucidating the relations between thyroid hormones, TSH, and weight fluctuations in children and adolescents at various stages of pubertal development.…”