Managing hyperthyroidism in pregnancy: current perspectives

Figures & data

Figure 1 Age-specific IR per 100,000 py for the most common types of hyperthyroidism in Denmark (Graves’ disease, multinodular toxic goiter, and solitary toxic adenoma).

Note: Reproduced with permission from Carlé A, Pedersen IB, Knudsen N, et al. Epidemiology of subtypes of hyperthyroidism in Denmark: a population-based study. Eur J Endocrinol. 2011;164(5):801–809.⁶
Abbreviations: IR, incidence rate; py, person-years.

Figure 2 IR of maternal hyperthyroidism in 3-month intervals before, during, and after the first pregnancy leading to birth of a live-born child from 1999 to 2008 in a Danish population-based study of 403,958 women.

Notes: The dashed horizontal line indicates the overall IR of maternal hyperthyroidism in women aged 15–45 years in the study period from 1997 to 2010. *Indicates significant difference from the overall IR. Republished with permission of the Endocrine Society, from Andersen SL, Olsen J, Carlé A, Laurberg P. Hyperthyroidism incidence fluctuates widely in and around pregnancy and is at variance with some other autoimmune diseases: a Danish population-based study. J Clin Endocrinol Metab. 2015;100(3):1164–1171;¹⁰ permission conveyed through Copyright Clearance Center, Inc.
Abbreviation: IR, incidence rate.

Figure 3 Reference limits for the diagnosis of hyperthyroidism in early pregnancy established with the Dimension Vista (Siemens) automatic immunoassay.

Notes: (A) and (B) illustrate the 2.5 percentile for TSH and the 97.5 percentile for fT4 with (95% CI), respectively. Dashed horizontal lines indicate the reference limit in nonpregnant adults as reported by the manufacturer. Republished with permission of the Endocrine Society, from Laurberg P, Andersen SL, Hindersson P, Nohr EA, Olsen J. Dynamics and predictors of serum TSH and fT4 reference limits in early pregnancy: a study within the Danish National Birth Cohort. J Clin Endocrinol Metab. 2016;101(6):2484–2492;¹⁶ permission conveyed through Copyright Clearance Center, Inc.
Abbreviations: TSH, thyroid-stimulating hormone; CI, confidence interval; fT4, free T4.

Figure 4 Adjusted OR with 95% CI for subtypes of birth defects in 1,097 children exposed to MMI/CMZ and 564 children exposed to PTU in early pregnancy versus the reference group of 811,730 children not exposed to ATD.

Notes: Musculoskeletal defects were various types of abdominal wall defects, integumentary defects included aplasia cutis and face and neck defects included preauricular sinus and cysts. Associations marked with gray circles were not statistically significant. Republished with permission of the Endocrine Society, from Andersen SL, Olsen J, Wu CS, Laurberg P. Birth defects after early pregnancy use of antithyroid drugs: a Danish nationwide study. J Clin Endocrinol Metab. 2013;98(11):4373–4381;⁴¹ permission conveyed through Copyright Clearance Center, Inc.
Abbreviations: OR, odds ratio; CI, confidence interval; MMI, methimazole; CMZ, carbimazole; PTU, propylthiouracil; ATD, antithyroid drug.

Table 1 Proposals on the treatment of hyperthyroidism in women who are or plan to become pregnant

Planned pregnancy

• Women who receive ATD treatment should contact the responsible physician if they are planning a pregnancy.

• When pregnancy is planned, treatment can be shifted to PTU before pregnancy, particularly in younger women with regular menses in whom rapid conception is likely.

• The conversion factor from MMI to PTU is 1:20, eg, 200 mg PTU per day replaces 10 mg MMI (or 15 mg CMZ).

Detected pregnancy

• Women who receive ATD treatment should be instructed to detect pregnancy as early as possible.

• Women who receive ATD treatment should perform a pregnancy test on the first days of a missing menstrual period, if pregnancy is a possibility.

• When pregnancy is detected, the woman should contact the responsible physician immediately to evaluate whether current ATD treatment should be continued, changed, or stopped.

• The responsible physician should evaluate the need for ATD treatment.

• If ATD treatment is considered necessary in the first trimester of pregnancy, PTU should be used.

• If ATD treatment is not considered necessary, weekly testing of thyroid function should be performed throughout the first trimester of pregnancy.

• If treatment is considered necessary after the first trimester of pregnancy, MMI/CMZ or PTU can be used.

Abbreviations: MMI, methimazole; CMZ, carbimazole; PTU, propylthiouracil; ATD, antithyroid drug.

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 PubMed Web of Science ®Google Scholar

AndersenSLOlsenJWuCSLaurbergPBirth defects after early pregnancy use of antithyroid drugs: a Danish nationwide studyJ Clin Endocrinol Metab201398114373438124151287

 PubMed Web of Science ®Google Scholar