Assessment of thyroid function during pregnancy: the advantage of self-sequential longitudinal reference intervals

Abstract

IntroductionTo evaluate clinical value of a new self-sequential longitudinal reference intervals of thyroid function during pregnancy.Material and methodsWe established two different series of reference intervals: self-sequential longitudinal reference intervals (SLRI) and general gestation-specific reference intervals (GSRI). For SLRI, the serum of 301 cases were collected five times in every case throughout the gestation. For GSRI, A total of 1455 subjects included in the study. We collected the serum respectively at various trimesters. We used TSH of both reference intervals to screen 1744 pregnant women, and compared the percentage of potential misclassification.ResultsBoth SLRI and GSRI differed substantially from that for non-pregnant women (p < 0.05). There are similar fluctuations of serum TSH, FT4 and TPO-Ab during normal pregnancy. Although there were no significant differences in most reference intervals between SLRI and GSRI. But the IQR of SLRI were usually smaller than GSRI , especially in 1st trimester. Two hundred and fifty two women (14.4%) at various trimesters whose serum TSH concentration was within SLRI would be misclassified, while 23 women (1.3%) with a TSH concentration outside limit would not be identified. 0.11-3.84% women would got thyroid diseases during pregnancy. Subclinical hypothyroidism is most common maternal thyroid disorders.ConclusionsThe SLRI can reflected the changes of thyroid function realistically, and can be used to decrease the percentage of potential misclassification of thyroid dysfunction during pregnancy. Screening for thyroid dysfunction of pregnant women is recommended and important.

Longitudinal evaluation of thyroid autoimmunity and function in pregnant Korean women

“…Direct comparison of our data to other published reports is problematic, as TFT reference intervals can be influenced by diet, maternal age, and assay methodology [e.g., 5,9,10,15]. It is well documented in the literature that using non-pregnant adult reference intervals to interpret TFT in pregnant women has the potential to result in a large number of misclassified test results [e.g., 6,7]. For these reasons, the American Thyroid Association (ATA) recommends using trimester specific reference intervals established in a population with optimal iodine intake [5].…”

“…Failure to do so can lead to potential misclassification of thyroid function tests (TFT) results in pregnant women [6,7]. Ideally, clinical laboratory test performance should be characterized using specimens representative of the patient population which the laboratory serves [8].…”

Late pregnancy thyroid-binding globulin predicts perinatal depression

“…Recent studies have established that the ranges of thyroid stimulating hormone (TSH) and free thyroxine (FT4) concentrations during pregnancy are lower than in non-pregnant women. FT4 levels are below the non-pregnant reference range in a substantial minority of pregnant women (Kurioka et al, 2005; Cotzias et al, 2008; Yu et al, 2010; Wang et al, 2011; Yan et al, 2011). The usual negative correlation between TSH and FT4 in non-pregnant women is lost during later pregnancy (Kurioka et al, 2005; Jonklass et al, 2009).…”

Maternal-Fetal Thyroid Interactions

“…THs are essential for normal neonatal development in both humans and rodents [3,23,[101][102][103][104] and the experimental work indicated that THs are transported from the mother to the fetus, albeit in limited amounts, and that the fetal brain is exposed to THs before initiation of fetal TH synthesis [1]. In addition, the maternal TH regulates early fetal brain development in human and animal models [2].…”