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Reference intervals from birth to adulthood for serum thyroxine (T4), triiodothyronine (T3), free T3, free T4,

M W Elmlinger1, W Kühnel, H G Lambrecht

  • 1University Children's Hospital, Paediatric Endocrinology Section, Tuebingen, Germany. martin.elmlinger@med.uni-tuebingen.de

Clinical Chemistry and Laboratory Medicine
|January 5, 2002
PubMed

Insights

Establishing pediatric thyroid hormone reference intervals is crucial for development. This study provides new reference ranges for thyroid-stimulating hormone (TSH) and thyroid hormones from birth to adulthood using automated chemiluminescence immunoassay.

Area of Science:

  • Pediatric Endocrinology
  • Clinical Chemistry
  • Immunoassay Technology

Background:

  • Thyroid dysfunction can significantly impact child development.
  • Establishing accurate reference intervals for thyroid hormones is essential for diagnosis and management in pediatric populations.
  • Existing reference ranges may not adequately cover the dynamic changes from birth through adolescence.

Purpose of the Study:

  • To establish comprehensive reference intervals for key thyroid hormones and thyrotropin (TSH) in euthyroid individuals from birth to adulthood.
  • To utilize the automated chemiluminescence immunoassay system (Immulite) for reliable and standardized measurements.
  • To provide age- and sex-specific reference data for clinical assessment.

Main Methods:

  • Serum samples from 762 euthyroid newborns, children, and adolescents (1 day to 19 years) were analyzed.
  • Measurements included triiodothyronine (T3), free T3 (fT3), thyroxine (T4), free T4 (fT4), thyroxine binding globulin (TBG), and TSH.
  • Non-normal distribution necessitated the calculation of 2.5th, 50th, and 97.5th percentiles for central 95% intervals.

Main Results:

  • Thyroid hormone and TSH concentrations showed significant variations, with higher medians in the neonatal period (up to 3.2-fold).
  • Thyroxine (T4) levels increased in the first month of life.
  • Thyroxine binding globulin (TBG) increased with age, peaking around 5 years, while other parameters generally decreased from 1 year onwards. No significant sex differences were observed.

Conclusions:

  • Reference intervals for thyroid hormones and TSH vary considerably after the neonatal period and across childhood and adolescence.
  • The established reference intervals are applicable for assessing thyroid status in pediatric patients using the Immulite/Immulite 2000 system.
  • Thyroid hormone levels do not correlate with sexual development, with the exception of a slight decrease in TBG during puberty.

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