Subclinical Thyroid Dysfunction in the First Trimester of Pregnancy

Disease' Versus Physiological (Pulsatile) Variation in TSH Concentrations

Krzysztof C. Lewandowski; Karolina Garnysz; Wojciech Horzelski; Joanna Kawalec; Karolina Budzen; Mariusz Grzesiak; Andrzej Lewinski


Clin Endocrinol. 2020;93(6):739-745. 

In This Article

Subjects and Methods

The study included 110 healthy pregnant women, age 30.2 ± 6.0 years, at 9.9 ± 2.4 weeks of gestation, BMI 24.9 ± 5.4 kg/m2, hospitalized in the Polish Mother's Memorial Hospital—Research Institute, between 2017 and 2019. The control group consisted of 19 nonpregnant healthy women, age 28.9 ± 10.7 years, BMI 28.3 ± 8.2 kg/m2, investigated in the Department of Endocrinology and Metabolic Diseases, Polish Mother's Memorial Hospital—Research Institute. We assessed baseline concentrations of free T4, free T3 and titres of antibodies against thyroid peroxidise (aTPO antibodies, reference range <34 IU/L); anti-thyroglobulin (aTg, reference range <115 IU/L); and anti-TSH receptor antibodies (aTSHR, reference range <1.8 IU/L), as well as TSH concentrations of TSH at 30-minute intervals (between 7.00 and 9.00 hours), that is in five consecutive samples.

Exclusion criteria encompassed previously known hypothyroidism or hyperthyroidism, as well as treatment with levothyroxine for any cause.

All samples were processed on COBAS e601 platform (Roche® Diagnostics), where the reference range for TSH is 0.27–4.2 mIU/L, interassay variation 3.5%, intra-assay variation 1.5% for euthyroidism (for mean TSH of 0.959 mIU/L); interassay variation 7.2%, intra-assay variation 3.0% for hyperthyroidism (mean TSH 0.04 mIU/L); and interassay variation 3.3%, intra-assay variation 1.1% for hypothyroidism (mean TSH 9.37 mIU/L).

The study was approved by the Ethics Committee of 'Polish Mother's Memorial Hospital—Research Institute (decision nr 78/2017).

Statistical Analysis

Statistical analysis was performed by means of MedCalc Software 12.6.1 software: MedCalc Software Ltd ©, Correlation analyses were performed using Pearson's coefficient or Spearman's rank correlation. The series measurement method and the Mann-Whitney test were used to compare TSH values at different time-points. P values <.05 were considered to indicate statistical significance.