Exploration of Physiological Reference Intervals for Thyroid Function During the First Trimester of Twin Pregnancy
Abstract
Objective:To explore specific reference intervals for serum thyroid-stimulating hormone (TSH) and free thyroxine (FT4) during the first trimester of twin pregnancies in Nanchong City and compare them with those of singleton pregnancies.
Methods:A retrospective analysis was conducted on 788 twin pregnancies who underwent prenatal examination and delivery at the Affiliated Hospital of North Sichuan Medical College from January 2017 to May 2024. Based on the criteria established by the National Academy of Clinical Biochemistry (NACB), 184 cases were included in the twin pregnancy group. Additionally, 537 singleton pregnancies from the same hospital and time period were randomly selected as the singleton group, and 42 twin pregnancies admitted between June and December 2024 were assigned as the non-concurrent validation group. Reference intervals for early pregnancy thyroid hormones were established using the percentile method, with the 2.5th (P2.5) and 97.5th percentiles (P97.5) of TSH and FT4 in the twin pregnancy group set as the lower and upper limits of normal thyroid function. Mann–Whitney U tests were used to compare differences between groups. The non-concurrent group was used to validate the preliminary reference intervals. The diagnostic discrepancies in thyroid dysfunction under different criteria were also analyzed.
结果: 妊娠早期双胎妊娠的 TSH 参考区间如下: 总 (T1) 0.005–4.28 mIU/L (中位数 1.15);孕周 1-6+6 (T1-1) 0.7-4.58 mIU/L(中位数 1.87);第 7-13+6 周 (T1-2) 0.004-4.11 mIU/L(中位数 0.78)。FT4 参考区间为:T1 0.98–2.60 ng/dl(中位数 1.29);T1-1 1.0–1.86 ng/dl(中位数 1.24);T1-2 0.97–2.68 ng/dl(中位数 1.32)。与单胎妊娠相比,双胎妊娠在妊娠早期表现出显着较低的 TSH 水平 (1.15 vs. 1.56 mIU/L,Z = –3.909,P < 0.01) 和较高的 FT4 水平 (1.29 vs. 1.27 ng/dl,Z = –2.882,P = 0.003)。这些差异在 T1-2 期间更为明显 (TSH: 0.78 vs. 1.25 mIU/L, Z = –3.723, P < 0.001;FT4:1.32 vs. 1.25 ng/dl,Z = –4.219,P < 0.01)。使用基于单例的参考区间或 2017 年美国甲状腺协会 (ATA) 指南导致双胎妊娠中亚临床甲状腺功能亢进症的严重过度诊断 (χ² = 34.833a,χ² = 31.233a,P < 0.01)。然而,与 ATA 2017 标准相比,应用双胞胎特异性参考区间降低了低 FT4 综合征的诊断 (χ² = 6.715a,P = 0.01)。
结论: 与单胎妊娠相比,南充市双胎妊娠早期甲状腺功能指标表现出明显的动态特征。建立双胞胎特异性参考区间至关重要。在双胎妊娠中,应用基于单胎或国际指南阈值可能会导致误诊和不适当的治疗,从而对母体和胎儿健康构成风险。因此,临床评估应优先采用为双胎妊娠量身定制的人群特异性参考标准。
Copyright (c) 2025 Xiangyu Liao, Xing Liang, Chongming Li, Qi Shi, Kerong Zhang

This work is licensed under a Creative Commons Attribution 4.0 International License.
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