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HYPOTHYROÏDIE et GROSSESSE
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Timing and Magnitude of Increases in Levothyroxine Requirements during Pregnancy in Women with Hypothyroidism
Erik K. Alexander, M.D., Ellen Marqusee, M.D., Jennifer Lawrence, M.D., Petr Jarolim, M.D., Ph.D., George A. Fischer, Ph.D., and P. Reed Larsen, M.D.
NEJM - Previous Volume 351:241-249 July 15, 2004 Number 3


: Les besoins en lévothyroxine sont augmentés en moyenne de 47 %. Le début de l'augmentation des besoins commence à la 8 ème semaine de gestation pour atteindre un plateau à la 16 ème semaine.
Les auteurs proposent l'adaptation thérapeutique suivante
  • pour une femme traitée pour hypothyroïdie qui a confirmation d'une grossesse débutante : augmentation immédiate d'environ 30% de la prise de lévothyroxine
  • Après plus de 5 semaines à cette nouvelle posologie, dosages biologiques, TSH et T4 libre, et nouvelle adaptation de posologie en fonction des résultats.
Voir également : Grossesse et thyroïde [Lire]

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Timing and Magnitude of Increases in Levothyroxine Requirements during Pregnancy in Women with Hypothyroidism
Erik K. Alexander, M.D., Ellen Marqusee, M.D., Jennifer Lawrence, M.D., Petr Jarolim, M.D., Ph.D., George A. Fischer, Ph.D., and P. Reed Larsen, M.D.
NEJM - Previous Volume 351:241-249 July 15, 2004 Number 3

ABSTRACT
Background Hypothyroidism during pregnancy has been associated with impaired cognitive development and increased fetal mortality. During pregnancy, maternal thyroid hormone requirements increase. Although it is known that women with hypothyroidism should increase their levothyroxine dose during pregnancy, biochemical hypothyroidism occurs in many. In this prospective study we attempted to identify precisely the timing and amount of levothyroxine adjustment required during pregnancy.

Methods
Women with hypothyroidism who were planning pregnancy were observed prospectively before and throughout their pregnancies. Thyroid function, human chorionic gonadotropin, and estradiol were measured before conception, approximately every two weeks during the first trimester, and monthly thereafter. The dose of levothyroxine was increased to maintain the thyrotropin concentration at preconception values throughout pregnancy.

Results
Twenty pregnancies occurred in 19 women and resulted in 17 full-term births. An increase in the levothyroxine dose was necessary during 17 pregnancies. The mean levothyroxine requirement increased 47 percent during the first half of pregnancy (median onset of increase, eight weeks of gestation) and plateaued by week 16. This increased dose was required until delivery.

Conclusions
Levothyroxine requirements increase as early as the fifth week of gestation. Given the importance of maternal euthyroidism for normal fetal cognitive development, we propose that women with hypothyroidism increase their levothyroxine dose by approximately 30 percent as soon as pregnancy is confirmed. Thereafter, serum thyrotropin levels should be monitored and the levothyroxine dose adjusted accordingly.

Source Information
From the Thyroid Section, Division of Endocrinology, Diabetes, and Hypertension, Department of Medicine (E.K.A., E.M., P.R.L.), and the Division of Clinical Laboratories, Department of Pathology (P.J., G.A.F.), Brigham and Women's Hospital and Harvard Medical School, Boston; and Valdosta Specialty Clinic, Valdosta, Ga. (J.L.).
Address reprint requests to Dr. Alexander at the Thyroid Section, Division of Endocrinology, Diabetes, and Hypertension, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 221 Longwood Ave., 2nd Fl., Boston, MA 02115, or at ekalexander@partners.org.