Evaluation of adherence to levothyroxine and out-of-range thyroid-stimulating hormone levels in pregnant women with primary hypothyroidism.

Abstract

Adherence to levothyroxine (LT4) and attaining thyroid-stimulating hormone (TSH) goal in pregnancy has not been well-defined yet. We aimed to investigate adherence to LT4, success to reach TSH goal, and association between them in pregnant women with primary hypothyroidism. Eight-item Morisky Medication Adherence Scale (MMAS-8) was applied in third trimester in pregnant women with primary hypothyroidism (Hashimoto's thyroiditis, surgical hypothyroidism or iodine deficiency) whom LT4 was given for at least 3months. Those with chronic illness or thyroid cancer were excluded. We grouped the patients according to MMAS-8 score (<6, low adherence vs ≥6, medium/high adherence), and TSH measurement in third trimester (in-range vs out-of-range). Of total (n=85), 57.64% (n=49) had medium/high adherence to LT4, and 41.17% (n=35) out-of-range TSH, but no association was found among them (P=.937). LT4 initiation in pregestational period, surgical hypothyroidism, high LT4 dose in second/third trimester and alternate-day dosing were associated with medium/high adherence. Age, number of visits, and less time between ingestion of LT4 and breakfast were associated with medium/high adherence. LT4 dose in second trimester and dose increment at the beginning of pregnancy were positively associated with in-range TSH. Non-adherence and treatment failure are frequent in LT4-treated pregnant women. Adherence seems not to be associated with treatment success. Regular follow-up may improve adherence. Our study is the first to analyse both treatment success and adherence to LT4 in pregnancy.