Postpartum Levothyroxine Adjustment and Its Impact Factors in Women With Hypothyroidism in Pregnancy

Abstract

Objective: Women with hypothyroidism need to increase exogenous thyroid hormone levels during pregnancy to reduce adverse outcomes. Few studies have reported the effect of gestational levothyroxine (LT4) variations on postpartum LT4 treatment.

Methods: Women were classified as having subclinical hypothyroidism (SCH) (n = 101), overt hypothyroidism (OH) caused by autoimmune thyroiditis (AIT-OH), OH following thyroidectomy for benign thyroid disease (BA-OH) (n = 66), and OH after surgery for papillary thyroid cancer (PTC-OH) (n = 46). Thyroid function was monitored, and LT4 therapy was adjusted accordingly.

Results: After delivery, all women with SCH stopped LT4 treatment, and 57.4% of them restarted LT4 treatment in the following 1 year, independently of the gestational LT4 variations. Among patients with OH, after adjusted by gestational body weight, 49.1% of them had LT4 doses less than the prepregnancy dose (baseline) in late pregnancy, leading to LT4 reduction in postpartum. The LT4 dose was reduced to approximately 50% baseline for women with AIT-OH and BA-OH and reduced by 27% for women with PTC-OH. The reduction reasons for AIT-OH and BA-OH were thyroid-stimulating hormone levels of <2.5 mU/L during pregnancy and postpartum thyrotoxicosis occurrence (39.4%), and for PTC-OH, the reason was thyroid-stimulating hormone overinhibition (<1.0 mU/L) before delivery.

Conclusion: For patients with SCH, postpartum LT4 treatment could initially be suspended. For women with OH, if the LT4 dose in late pregnancy was less than baseline, a prepregnancy dose reduced by 50%, 50%, and 27% should be applied after delivery for women with AIT-OH, BA-OH, and PTC-OH, respectively.

Keywords: hypothyroidism; levothyroxine; postpartum; pregnancy; thyroid-stimulating hormone.