Reference Values for TSH and Free Thyroid Hormones in Healthy Pregnant Women in Poland: A Prospective, Multicenter Study

Abstract

Objectives: The diagnosis and treatment of thyroid diseases in pregnant women remains a challenge. Various medical associations recommend establishing the reference intervals for thyroid hormones by a local laboratory. Considering differences within geophysical, socioeconomic conditions, and iodine prophylaxis in various populations, it is advisable to assess reference intervals for thyroid hormones specific to a region of residence. The objective was to assess trimester-specific reference intervals for TSH, fT₃, and fT₄ for pregnant women in the Polish population. Methods and Results: We conducted a prospective study in 4 centers representing different regions of Poland (Krakow, Warsaw, Poznan, and Bialystok). Our study included consecutive, healthy pregnant women (172 patients), with an age range of 27-47 years. All women had a negative history for thyroid diseases, normal thyroid peroxidase antibody levels, and proper iodine prophylaxis. All newborns had TSH levels in the appropriate reference range. Serum TSH, fT₃, fT₄, and thyroid-peroxidase antibodies were measured in each trimester. The reference intervals were calculated using the percentile method, as recommended by the International Federation of Clinical Chemistry. The reference values calculated were 0.009-3.177, 0.05-3.442, and 0.11-3.53 mIU/L for TSH; 3.63-6.55, 3.29-5.45, and 3.1-5.37 pmol/L for fT₃; and 11.99-21.89, 10.46-16.67, and 8.96-17.23 pmol/L for fT₄ in consecutive trimesters of pregnancy. Reference intervals for pregnant women when compared to the general population showed a lower concentration of TSH in every trimester of pregnancy and lower fT₄ in the 2nd and 3rd trimesters. Conclusions: Using appropriate trimester-specific reference intervals may improve care of pregnant women by preventing misdiagnosis and inadequate treatment.

Reference Intervals of Thyroid Hormones and Correlation of BMI with Thyroid Function in Healthy Zhuang Ethnic Pregnant Women

“…These results are in line with the observations in other studies [ 28 ]. Our reference intervals for FT4 in the three trimesters were close to the reference ranges for Polish women (11.99–21.89, 10.46–16.67, and 8.96–17.23 pmol/L, respectively) [ 29 ] but wider than the reference intervals in the pregnant women of West China (12.29–18.92, 10.97–15.49, and 9.49–16.25 pmol/L, respectively) [ 27 ]. Our reference intervals for FT3 were similar to those of Kosteckamatyja, who used the same assay.…”

“…Kosteckamatyja et al . determined that the trimester-specific reference intervals for FT3 of Polish pregnant women were in the ranges of 3.6–6.5, 3.3–5.5, and 3.1–5.4 pmol/L in the first, second, and third trimesters, respectively [ 29 ]. The differences in the reference intervals were probably due to diversity in several factors, such as measurement techniques, ethnic, sample size, selection criteria, sample processing, population-specific characteristics, and variation in iodine intake.…”

Establishment of assay method- and trimester-specific reference intervals for thyroid hormones during pregnancy in Chengdu, China

“…However, the reference intervals for thyroid hormones are generally based on the reference intervals provided by manufacturers or other laboratory or reference literature, which usually leads to confusing results in clinical practice. Therefore, many medical associations, including the Chinese Society of Endocrinology and the Chinese Society of Perinatal Medicine, suggest that laboratory-and geography-speci c reference intervals for thyroid hormones should be established by a local laboratory [19,20]. The 2017 ATA guidelines have also strongly recommended that population-based trimester-speci c reference intervals for serum thyroid hormones during pregnancy should be de ned by a provider's laboratory and should represent the typical population for whom care is provided [11].…”

Płodowa niedoczynność tarczycy z wolem — łatwo rozpoznać, trudno leczyć. Czy podawanie doowodniowe i dożylne L-tyroksyny jest jedną z opcji terapeutycznych?

“…Foetal blood TSH concentration was 1500 µIU/mL (n. 6.8 ± 2.93 µIU/mL), fT3 -0.87 pmol/L (n. 0.2-0.5 pmol/L), fT4 -2.0 pmol/L (n. 16.5 ± 5.3 pmol/L) [6,7], thyroglobulin 1500 ng/mL (n. 0.55 ng/mL), and pro-BNP 1247 ng/mL (n. 0.125 ng/ /mL). Evaluation of the maternal thyroid status showed normal TSH 2.357 µIU/mL (n. 0.05-3.44 µIU/L) and fT4 13.59 pmol/L (n. 10.46-16.67 pmol/L) [8], negative antiperoxidase (a-TPO) < 37 IU/mL (n. 0.60 IU/mL), antithyroglobulin (aTg) < 25 IU/mL (n.0-60 IU/mL), and anti-TSH receptor antibodies 0.42 IU/L (n. < 1.8 IU/L), no signs of excessive iodine excretion in urine, and normal thyroid US scan. Intra-amniotic treatment with L-T4 was started from 24 WG: the first dose was 500 µg, followed by two doses of 250 µg given in weekly intervals.…”