. 2022 Aug 9;46(1):15–26. doi: 10.1007/s40618-022-01883-7

Table 1.

Reference limits of TSH and thyroid hormones dosage in pregnancy according to Guidelines

	2014 European thyroid association guidelines	2017 American thyroid association guidelines
TSH	- Trimester-specific reference ranges should be established in each laboratory. Local variations may occur - If not available, the following reference range are recommended: first trimester upper limits 2.5 mU/L; second trimester upper limits 3.0 mU/L; third trimester upper limits 3.5 mU/L	- Reference range for each trimester adjusted for the population Or - TSH < 4 mU/mL
fT4 T4	-T4 and fT4 assays are both suitable for thyroid function testing in pregnancy	-T4 analysis is suitable instead of fT4
fT3 T3	-	-T3 analysis could be helpful in the diagnosis and management of hyperthyroidism, in the presence of suppressed TSH

2014 European thyroid association guidelines

2017 American thyroid association guidelines

TSH

- Trimester-specific reference ranges should be established in each laboratory. Local variations may occur

- If not available, the following reference range are recommended: first trimester upper limits 2.5 mU/L; second trimester upper limits 3.0 mU/L; third trimester upper limits 3.5 mU/L

- Reference range for each trimester adjusted for the population

- TSH < 4 mU/mL

fT4

-T4 and fT4 assays are both suitable for thyroid function testing in pregnancy

-T4 analysis is suitable instead of fT4

fT3

-T3 analysis could be helpful in the diagnosis and management of hyperthyroidism, in the presence of suppressed TSH

TSH thyroid-stimulating hormone, fT4 free thyroxine, fT3 free triiodothyronine