Thyroxine Supplementation in Pregnant Women After Thyroidectomy for Thyroid Cancer and Neonatal Birth Weight.

Zheng Ding,Jianxia Fan,Xiaoyi Huang,Fei Guo,Zhiwei Liu,Yulai Zhou

doi:10.3389/fendo.2021.728199

Abstract

Patients are often supplemented with a sufficient dose of thyroxine after thyroidectomy for thyroid cancer. However, the influence of thyroxine supplementation on fetal growth in pregnant women after thyroidectomy for thyroid cancer remains unclear. The aim of this study was to investigate the effect of thyroxine supplementation on neonatal birth weight. This cohort study included 49,896 pregnant women (278 patients with a history of thyroidectomy for thyroid cancer and 39,363 control cases after exclusion). Thyroid parameters were examined in pregnant women and their newborns. The associations between maternal thyroid function and neonatal birth weight and small for gestational age were studied using regression analyses. In the levothyroxine supplementation group, free thyroxine (FT4) levels were significantly higher in both early pregnancy (P < 0.001) and late pregnancy (P < 0.001) groups than in the control group. Furthermore, levels of neonatal thyroid stimulating hormone (P = 0.032) and birth weight (P = 0.043) were significantly lower than those in the control group. We also observed a significant inverse association between maternal FT4 levels in early pregnancy and neonatal birth weight (P=0.028), especially in male newborns (P=0.036). In summary, after thyroidectomy for thyroid cancer, a sufficient dose of thyroxine supplementation in early pregnancy is significantly associated with reduced birth weight and may need to be monitored.

Highlights

Thyroid cancer is a common endocrine malignancy in young women
278 patients underwent a total thyroidectomy due to papillary thyroid cancer and they required a sufficient dose of LT4 for replacement treatment or the thyroid stimulating hormone (TSH) suppression
We found a difference in the TSH level of neonatal plantar blood within a week of birth between the two groups, and the mean neonatal TSH level was lower in the LT4 supplementation group than in the control group

Summary

Introduction

Thyroid cancer is a common endocrine malignancy in young women. The prevalence of thyroid cancer in pregnancy (14.4/100,000) was reported [1], and 3.3/100,000 was diagnosed before delivery [2]. Women of childbearing age are concerned because of their potential influence on the fetus. Women usually undergo thyroidectomy for thyroid cancer. Thyroid hormone replacement or thyroid stimulating hormone (TSH) suppression therapy with levothyroxine (LT4) to prevent hypothyroidism or tumor recurrence is needed. It is often difficult to adjust the dose of the drug to maintain an ideal thyroxine level in clinical practice, especially in pregnant women. Few studies have examined the effect of maternal thyroxine supplementation on fetal growth in women with a history of thyroidectomy for thyroid cancer

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