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Cited by 360Thyroid Disorders and TreatmentsThyroid and Parathyroid SurgeryThyroid Cancer Diagnosis and Treatment

Increased need for thyroxine during pregnancy in women with primary hypothyroidism

Mandel, Susan J., Larsen, P. Reed, Seely, Ellen W., Brent, Gregory A.·1990·New England Journal of Medicine
DOI 10.1056/nejm199007123230204
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Abstract

BACKGROUND AND METHODS: Women with hypothyroidism have been thought not to require an increase in thyroxine replacement during pregnancy. To evaluate the effects of pregnancy on thyroxine requirements, we retrospectively reviewed the thyroid function of 12 women receiving treatment for primary hypothyroidism before, during, and after pregnancy. RESULTS: In all patients, the serum thyrotropin level increased during pregnancy. The mean (+/- SE) serum free-thyroxine index decreased from 111.0 +/- 5.8 before pregnancy to 86.5 +/- 5.2 during pregnancy (normal, 64 to 142; P less than 0.05), and the mean serum thyrotropin level increased from 2.0 +/- 0.5 mU per liter before pregnancy to 13.5 +/- 3.3 mU per liter during pregnancy (normal, 0.5 to 5.0 mU per liter; P less than 0.01). Because of high thyrotropin levels, the thyroxine dose was increased in 9 of the 12 patients. Among the three patients who did not require an increased thyroxine dose were two with low serum thyrotropin levels before pregnancy, suggesting excessive replacement at that time. The mean thyroxine dose before pregnancy was 0.102 +/- 0.009 mg per day; it was increased to 0.148 +/- 0.015 mg per day during pregnancy (P less than 0.01). The mean postpartum serum free-thyroxine index was 136.6 +/- 11.4 (P less than 0.05 as compared with values before and during pregnancy), and the mean postpartum serum thyrotropin level was 1.4 +/- 0.4 mU per liter (P less than 0.01 as compared with levels during pregnancy), demonstrating a decrease in the thyroxine requirement. The mean postpartum thyroxine dose was decreased to 0.117 +/- 0.011 mg per day (P less than 0.01 as compared with the dose during pregnancy). CONCLUSIONS: Our results indicate that the need for thyroxine increases in many women with primary hypothyroidism when they are pregnant, as reflected by an increase in serum thyrotropin concentrations. Although the effects of this modest level of hypothyroidism are not known, we think it prudent to monitor thyroid function throughout gestation and after delivery and to adjust the thyroxine dose to maintain a normal serum thyrotropin level.

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Crossref · 10.1056/nejm199007123230204

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  • An increased need for thyroxine has been observed in pregnant patients.

    “Similarly, an increased need for thyroxine has also been observed in pregnant patients (61).”

    From Levothyroxine: conventional and novel drug delivery formulations. (2023) · cites this paper as [61]

  • Liquid solutions also alleviate the malabsorption induced by some nongastrointestinal disorders, such as nephrotic syndrome and pregnancy.

    “Surprisingly, liquid solutions also alleviate the malabsorption induced by some nongastrointestinal disorders, such as nephrotic syndrome (35, 36) and pregnancy (61).”

    From Levothyroxine: conventional and novel drug delivery formulations. (2023) · cites this paper as [61]

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Authors
Mandel, S. J., Larsen, P. R., Seely, E. W., & Brent, G. A.
Affiliations
Brigham and Women's Hospital (US)
ORCID
Venue
New England Journal of Medicine
Publisher
Massachusetts Medical Society
Published
1990-07-12
Volume
323
Issue
2
Pages
91-96
ISSN
  • 0028-4793 (ISSN-L)
  • 1533-4406
DOI
10.1056/nejm199007123230204
OpenAlex
W3021125997
Cited by
360
References
15
Citations by year
2026: 2 · 2025: 2 · 2024: 3 · 2023: 2 · 2022: 7 · 2021: 3 · 2020: 8 · 2019: 5 · 2018: 4 · 2017: 11 · 2016: 6 · 2015: 15 · 2014: 13 · 2013: 13 · 2012: 18
FWCI
7.25
Type
journal article
Language
en
Open access
closed
Locations
  • New England Journal of Medicine (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Institutes of Health (1k12am001401-01)
  • National Heart, Lung, and Blood Institute (T32HL007609, 5 T32 HL07609)
  • National Institute of Diabetes and Digestive and Kidney Diseases (DK36256, R01DK036256)
Topics
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
  • Health Sciences › Medicine › Surgery › Thyroid and Parathyroid Surgery
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Cancer Diagnosis and Treatment
Keywords
primary hypothyroidism, pregnancy, levothyroxine replacement, thyroid-stimulating hormone, free thyroxine index, postpartum thyroid function, thyroid function monitoring
MeSH terms
Female, Humans, Hypothyroidism, Pregnancy, Pregnancy Complications, Retrospective Studies, Thyroid Gland, Thyrotropin, Thyroxine, Postpartum Period

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