Thyroid function reference ranges during pregnancy in a large Chinese population and comparison with current guidelines

Abstract

Background:A correct thyroid function reference range is important for the accurate diagnosis of thyroid disease during pregnancy. However, there is no consensus on whether thyroid function reference ranges in Chinese population should follow the America Thyroid Association (ATA) guidelines. This study aimed to establish a thyroid function reference range more suited to the Chinese population by evaluating the current thyroid function reference range in pregnant Chinese women and comparing it to the ATA guidelines.Methods:A total of 52,027 pregnant women were enrolled from January 2013 to December 2016. Thyroid stimulating hormone (TSH), free thyroxine (FT4), and thyroid peroxidase antibody (TPOAb) levels were tested during the first and third trimesters of pregnancy. Reference ranges of TSH and FT4 were established from the 2.5th and 97.5th percentiles of the TPOAb-negative population of women. The Mann-Whitney U test was used to compare thyroid hormones between the TPOAb-positive and TPOAb-negative groups.Results:We obtained that the TSH reference ranges were 0.03 to 3.52 mU/L and 0.39 to 3.67 mU/L, and the FT4 reference ranges were 11.7 to 19.7 pmol/L and 9.1 to 14.4 pmol/L, in the first and third trimester, respectively. If we used the 2011 ATA criteria about 7.0% and 4.0% pregnant women would be over diagnosed in first and third trimester, respectively, compared with local population thyroid hormone reference. When we compared our local criteria with the new 2017 ATA criteria, about 1.2% and 0.8% pregnant women would have a missed diagnosis in first and third trimester, respectively.Conclusions:Based on our data, which is in line with the current ATA guidelines, a population-based thyroid function reference range would be the first choice for diagnosis of thyroid disease during pregnancy in China. In case such population-based thyroid function reference ranges are unavailable in the east of China, our reference ranges can be adopted, if the same assay is used.Trial Registration:www.chictr.org.cn (No. ChiCTR1800014394).

Subclinical thyroid dysfunction in the first trimester of pregnancy: ‘Disease’ versus physiological (pulsatile) variation in TSH concentrations

“…As mentioned above, there is no consensus regarding the TSH reference range in pregnancy. For instance, in a recent study from China, based on a data from 46 262 pregnant women 9 the authors suggested a TSH reference range of 0.03‐3.52 mIU/L, for aTPO‐negative women, while among aTPO‐positive women (n = 4628, ie about 10% of the total), first‐trimester TSH ‘reference range’ was 0.05‐4.57 mIU/L. Similar observations suggesting TSH reference range of 0.005‐3.65 mIU/L are based on data from Turkey (n = 1258) 10 .…”

“…Despite the plethora of papers pertaining to thyroid hormone reference ranges in pregnancy, available studies are effectively based on single thyroid hormone measurement 9‐11,13,16,17 . This applies also to affluent European countries, such as Denmark, where thyroid function and aTPO status were recently assessed in 14 323 pregnant women in the first trimester of pregnancy 24 …”

Antithyroid Peroxidase Antibodies and Histopathological Outcomes in Egyptian Patients Subjected to Total Thyroidectomy for Nonmalignant Nodular Goiter

“…Previous studies demonstrated that thyroid antibodies are not common in children. Female gender and puberty are strongly associated with thyroid antibody development [18,19]. The autoantibodies showed a tendency to increase with age [20].…”

Antithyroid Peroxidase Antibodies and Histopathological Outcomes in Egyptian Patients Subjected to Total Thyroidectomy for Non-Malignant Nodular Goiter

“…Female gender and puberty are strongly associated with thyroid antibody development. 18 , 19 The autoantibodies showed a tendency to increase with age. 20 It was shown that 21% of women of the Whickham cohort coveted to thyroid antibody positivity around the age of menopause.…”