Is TSH a Reliable Indicator of Thyroid Hormone Status in
                    Pregnancy?

Gilad Karavani; Lina Daoud-Sabag; Cherut Chay; David Gillis; David Strich

doi:10.1055/a-1872-0246

Hormone and Metabolic Research, Table of Contents

Horm Metab Res 2022; 54(07): 435-441
DOI: 10.1055/a-1872-0246

Original Article: Endocrine Care

Is TSH a Reliable Indicator of Thyroid Hormone Status in Pregnancy?

Gilad Karavani

¹Department of Obstetrics and Gynecology, Hadassah Ein-Kerem Medical Center and Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel

²Infertility and IVF Unit, Hadassah Ein-Kerem Medical Center and Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel

,

Lina Daoud-Sabag

¹Department of Obstetrics and Gynecology, Hadassah Ein-Kerem Medical Center and Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel

,

Cherut Chay

³Department of Family Medicine, Technion Israel Institute of Technology Ruth and Bruce Rappaport Faculty of Medicine, Tel Aviv, Israel

,

David Gillis

⁴Department of Pediatrics, Hadassah-Hebrew University Medical Center, Jerusalem, Israel

⁵Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel

,

David Strich

⁵Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel

⁶Pediatrics, Shaare Zedek Medical Center, Jerusalem, Israel

⁷Pediatric Specialties, Shaare Zedek Medical Center, Jerusalem, Israel

› Author Affiliations

Abstract

Thyroid screening is recommended during pregnancy with serum thyrotropin (TSH) as the primary test. However, since human chorionic gonadotropin, the serum hallmark of pregnancy, has TSH-like effects, the adequacy of TSH as a screening tool in this constellation requires further study. This study aimed to evaluate the relationship between TSH and thyroid hormones during pregnancy in order to determine if TSH is an adequate screening tool. This was a retrospective study utilizing the Clalit Health Service, Jerusalem district database between 2006–2017 in which we analyzed TSH, FT4 and FT3 measurements from 32430 pregnancies resulting in live birth. We grouped FT4 and FT3 levels by trimester and by the following TSH levels: (1) below 0.1/0.2/0.3 mIU/l, (2) 0.1–2.5/0.2–3.0/0.3–3.0 mIU/l, (3) 2.6–4.0/3.1–4.0 mIU/l, (4) 4.1–10.0 mIU/l and (5) above 10.0 mIU/l. In the first trimester, the most important for fetal brain development, FT3 was below normal, defined as below the 2.5th percentile for the population, in only 15.3% of tests with TSH over 10 mIU/l. FT4 was below normal in only 12.8% of such tests. Similar findings were noted for the second and third trimesters. As expected, there were far less abnormal tests when lower TSH cutoff levels were tested. In conclusion, TSH levels beyond the range accepted as normal do not, in most cases, reflect abnormal thyroid hormone levels during pregnancy. TSH is not a good screen for overt hypothyroidism in pregnancy. This may be due, at least in the first trimester, to thyrotropic effects of HCG.

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References

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