| Objective:Setting up the gestational trimester-specific reference intervals of thyroid hormones and TPOAb for normal pregnant women in Kunming, which can help to screen, diagnose, treat and monitor thyroid disease during pregnancy and make related research.Methodsr:Our study have two phases:(1)Study population in Group A was retrospective and cross-sectional population-based cohort(N=17,282),according to some criterion, a total of16,172normal cases were selected from the17,282pregnant women who had only got serum TSH screening from January2004to December2011by CMIA, and then establish gestational trimester-specific reference intervals of TSH with the statistical method of percentile.(2)Study population in Group B was also retrospective and cross-sectional population-based cohort(N=3,821),in which, pregnant women got the serum TSH,FT4and TPOAb screening from June to December in2012by CMIA. According to the TSH reference intervals established in Group A, a total of3,500normal TSH cases were selected from the3,821pregnant women to establish gestational trimester-specific reference intervals of TPOAb with the statistical method of percentile; according to the TSH reference intervals established in Group A and the TPOAb reference intervals established in Group B, a total of3,327normal TSH and normal TPOAb cases were selected from the3,821pregnant women to establish gestational trimester-specific reference intervals of FT4with the statistical method of percentile. Beyond that, TPOAb positive rate, hypothyroidism morbidity and subclinical hypothyroidism morbidity had also been calculated. TSH and FT4reference intervals use the median (M) and95%CI(P25-P97.5),TPOAb reference interval use90%CI(P5-P95); TPOAb positive rate, hypothyroidism and subclinical hypothyroidism morbidity use rate (%). Results:(1) During pregnancy, serum TSH level decreased obviously in the first trimester, and dropped to the lowest level at9-12weeks,then it began to rebound and leveled off. After37weeks the TSH level is slightly rising.(2)The gestational trimester-specific reference intervals of thyroid hormones and TPOAb were as follows:TSH95%CI:T1,1.59(0.1-4.73) mIU/L,T2,1.88(0.33-4.66) mIU/L,T3,2.11(0.67-4.95) mIU/L; FT495%CI:T1,11.00(8.24-15.06) pmol/L,T2,9.25(6.66-12.99) pmol/L, T3,7.52(5.56-10.62) pmol/L; TPOAb90%CI:T1,(0.1-81) IU/mL, T2,(0.1-68)IU/mL,T3,(0.1-50)IU/mL.(3)TPOAb positive rate is6.1%(232/3821),including of T1,6.7%(82/1231),T2,5.9%(55/925),T3,5.7%(95/1665);hypothyroidism morbidity is0.34%(13/3821), including of T1,0.6%(8/1231), T2,0.3%(3/925), T3,0.1%(2/1665); subclinical hypothyroidism morbidity is3.7%(140/3821),including of T1,4.6%(57/1231), T2,2.8%(26/925), T3,4.0%(67/1665).(4) Whatever the level of serum TSH is normal or abnormal, serum TPOAb maybe positive in pregnant women, the pregnant women with thyroid function deficiency(including of hypothyroidism and subclinical hypothyroidism) had a high TPOAb positive rate(21.0%).(5) The hypothyroidism morbidity in pregnant women with TPOAb positive and negative were separately2.6%and0.2%; the subclinical hypothyroidism morbidity in pregnant women with TPOAb positive and negative were separately11.6%and3.1%.Conclusion:(1)This study has collected the largest samples to do epidemiological investigation in China at now.We have established the gestational trimester-specific reference intervals for serum TSH,FT4and TPOAb.We also get the TPOAb positive rate, hypothyroidism and subclincal hypothyroidism morbidity in Kunming for the first time.(2) Thyroid function indexes fluctuated profoundly during pregnancy and it is essential to establish trimester-specific reference intervals for appropriate diagnosis of thyroid disease during pregnancy.(3) TPOAb can prompt the risk for autoimmune thyroid disease in pregnancy,and thyroid function should be monitored closely in the pregnant women with positive TPOAb. |
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