FT4 Reference Range for Neonates Under 1 Month

Essential Clinical Caveats

• Reference ranges vary significantly between different immunoassay platforms and manufacturers, emphasizing the need to use assay-specific ranges 1
• The American College of Medical Genetics recommends always using the reference range established by your specific laboratory using their exact analyzer and reagent system to avoid misdiagnosis 2
• The Endocrine Society suggests that FT4 must always be interpreted in conjunction with TSH levels for comprehensive assessment, considering that in congenital hypothyroidism of thyroidal origin, TSH is elevated with low FT4, while central hypothyroidism shows low FT4 without clearly elevated TSH 1, 3