title: Levothyroxine Dosage Requirement During Pregnancy in Well-Controlled Hypothyroid Women: A Longitudinal Study.
abstract: BACKGROUND
  Untreated maternal hypothyroidism can have adverse effects on both the mother and fetus, but it can potentially be prevented by adequate levothyroxine replacement. This study was conducted to determine what percentage of hypothyroid pregnant women who were taking levothyroxine needed to adjust their medication dosage, and when and how much it should be increased.
  
  
  METHODS
  In this longitudinal study, 81 well-controlled hypothyroid women (TSH≤ 2.5 mIU/L) were monitored throughout pregnancy. Thyroid function tests were performed before conception, after the first missed menstrual period, in the second and third trimesters of pregnancy and one month after delivery. Levothyroxine dosage was adjusted according to TSH levels measured.
  
  
  RESULTS
  Of the 81 pregnancies studied, the pregnancy outcomes were 74 full-term births, six abortions and one pre-term birth. The levothyroxine dosage needed to be increased in 84% (CI95%= 74-90) of the pregnancies (OR=5.2, CI95%= 2.9-9.4). Most levothyroxine dose adjustments were made in the first trimester of gestation. The levothyroxine requirement increased 50% (CI95%= 41-59) in the first trimester, 55% (CI95%= 45-64) in the second trimester and 62% (CI95%= 52-72) in the third trimester. Levothyroxine dosage was decreased for 6 cases (7.4%), and no adjustment was made for 7 women (8.6%).
  
  
  CONCLUSIONS
  Increases in levothyroxine dosage administered in pregnancy appear to be indispensible in the majority of patients with well-controlled hypothyroidism, especially in the first trimester. However, this change was not universal and levothyroxine dosage decreased in a few cases and remained unchanged in others.
authors.affiliation: Diabetes Research Center, Mazandaran University of Medical Sciences, Sari, Iran. kashi_zahra@yahoo.com.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Kashi
authors.forename: Adele
authors.initials: A
authors.lastname: Bahar
authors.forename: Ozra
authors.initials: O
authors.lastname: Akha
authors.forename: Samane
authors.initials: S
authors.lastname: Hassanzade
authors.forename: Leila
authors.initials: L
authors.lastname: Esmaeilisaraji
authors.forename: Zeinab
authors.initials: Z
authors.lastname: Hamzehgardeshi
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy*; D007492:Iran; D008137:Longitudinal Studies; D011247:Pregnancy; D011248:Pregnancy Complications / Q000188:drug therapy*; D011256:Pregnancy Outcome; D013974:Thyroxine / Q000008:administration & dosage*; D016896:Treatment Outcome
chemical_list: D013974:Thyroxine