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 Table of Contents  
Year : 2017  |  Volume : 14  |  Issue : 3  |  Page : 97-98

Preconception advice to hyperthyroid women

1 Department of Thyroid and Endocrine Research, Institute of Nuclear Medicine and Allied Sciences, DRDO, New Delhi, India
2 Department of Endocrinology, Bharti Hospital and Bride, Karnal, Haryana, India

Date of Web Publication9-Oct-2017

Correspondence Address:
Rashmi Aggarwal
Department of Thyroid and Endocrine Research, Institute of Nuclear Medicine and Allied Sciences, DRDO, New Delhi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/trp.trp_33_17

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Uncontrolled or untreated hyperthyroidism in pregnancy may have adverse outcomes both in mother as well as her fetus. The mother is at increased risk of miscarriage, abruptio placentae, heart failure, and thyroid storm. The neonate is at increased risk of still birth or developing fetal and neonatal hyperthyroidism. Women with Graves' disease or those suffering from any other causes of hyperthyroid should be given reassurance and preconception advice before their becoming pregnant. Antithyroid drugs are the main therapy for maternal hyperthyroidism. This article shall focus on the choice of antithyroid medication that can be used in different trimesters of pregnancy. The patient should also be reminded to undergo thyroid function test in the postpartum period as well.

Keywords: Carbimazole, Graves' disease, lactation, pregnancy, propylthiouracil

How to cite this article:
Aggarwal R, Kalra S. Preconception advice to hyperthyroid women. Thyroid Res Pract 2017;14:97-8

How to cite this URL:
Aggarwal R, Kalra S. Preconception advice to hyperthyroid women. Thyroid Res Pract [serial online] 2017 [cited 2022 Nov 29];14:97-8. Available from: https://www.thetrp.net/text.asp?2017/14/3/97/216211

  Introduction Top

Hyperthyroidism occurs in 0.1%–0.4% of pregnancies and is most commonly due to Graves' disease. Untreated hyperthyroidism has potentially serious adverse effects both on the mother and her fetus. The mother is at increased risk of miscarriage, abruptio placentae, preterm labor, heart failure, and thyroid storm.[1] The fetus is at increased risk of spontaneous abortion, intrauterine growth retardation, still birth, and congenital malformations. To prevent these undesirable fetal and maternal outcomes, meticulous, prompt, and careful management of hyperthyroidism throughout pregnancy is needed.

  Preconception and Intraconception Advice Top

All hyperthyroid women willing to become pregnant should be given following instructions:

  1. To perform a pregnancy test a week after missed period and if it turns out to be positive, they should see their health-care provider immediately and on the same day
  2. They should immediately undergo a thyroid function test, and if they are found to be in remission, no antithyroid medication is needed, but they should be followed up with frequent thyroid function test, especially in each trimester
  3. If they are not in remission, then they should be started with propylthiouracil (PTU) in the first trimester and then shift to carbimazole/methimazole (MMI) in the second trimester and then continue with that even in the postpartum period [2]
  4. If the pregnant woman is on carbimazole, then immediately shift her to PTU
  5. The mother should also be informed about the side effects of carbimazole, its active metabolite MMI, and PTU
  6. All pregnant women on anti thyroid drugs (ATD) should be told to contact their health-care provider if they experience the following symptoms: fever with sore throat, fatigue, loss of appetite, itching, and yellowish appearance of eyes or skin
  7. Thyroid function test at regular intervals should be monitored and adjust of the doses of antithyroid drugs should be monitored if needed
  8. Serial ultrasound of the fetus to look for fetal goiter should be performed
  9. The pediatrician should also be informed that the mother is hyperthyroid and so the neonate may be at risk of developing hyperthyroidism and so the infant may be checked for thyroid dysfunction.

  Adverse Effects of Antithyroid Medications Top

Carbimazole or its active metabolite MMI when taken by the pregnant women in the first trimester of pregnancy is associated with development of a syndrome in the fetus called MMI embryopathy. This includes choanal atresia, esophageal atresia, tracheoesophageal fistula, aplasia cutis, and dysmorphic facial features.[3]

PTU can cause fulminant hepatic necrosis that can be fatal and so the US Food and Drug Administration has issued a black box warning against the use of PTU, and it is to be used only in the first trimester of pregnancy. Because of the potential of development of congenital malformation with the use of carbimazole/MMI, PTU is the drug of choice to be used in the first trimester of pregnancy which is actually the period of organogenesis. Thereafter, the pregnant mother is shifted back to carbimazole or MMI, and PTU is withdrawn because of the association of serious liver toxicity with the use of PTU.

While the pregnant women are on antithyroid medications, her free T4 and TSH should be measured almost every 2–4 weeks at the time of initiation of therapy and then every 4–6 weeks thereafter.

Doses of antithyroid medications should be maintained at the lowest doses so as to keep the free T4 of the mother in the high normal range.

  Breastfeeding Top

Breastfeeding should be encouraged even if the mother is on antithyroid medications. Both carbimazole and PTU are secreted in human milk. Carbimazole in a dose of 20–30 mg/day and PTU up to 300 mg/day are considered to be safe with negligible risk to the infant. Dose of antithyroid medication should be taken immediately after nursing (feeding) and then waiting for 3–4 h before feeding again.[4] MMI is the mainstay of treatment of postpartum hyperthyroidism, especially during lactation.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Aggarwal R, Chugh P. Management of hyperthyroidism in pregnancy. Int J Reprod Contracept Obstet Gynecol 2016;5:1-5.  Back to cited text no. 1
Barbero P, Valdez R, Rodríguez H, Tiscornia C, Mansilla E, Allons A, et al. Choanal atresia associated with maternal hyperthyroidism treated with methimazole: A case-control study. Am J Med Genet A 2008;146A: 2390-5.  Back to cited text no. 2
Emiliano AB, Governale L, Parks M, Cooper DS. Shifts in propylthiouracil and methimazole prescribing practices: Antithyroid drug use in the United States from 1991 to 2008. J Clin Endocrinol Metab 2010;95:2227-33.  Back to cited text no. 3
Azizi F, Amouzegar A. Management of hyperthyroidism during pregnancy and lactation. Eur J Endocrinol 2011;164:871-6.  Back to cited text no. 4


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