The Relationship of Preconception Thyrotropin Levels to Requirements for Increasing the Levothyroxine Dose During Pregnancy in Women with Primary Hypothyroidism.
Summary of "The Relationship of Preconception Thyrotropin Levels to Requirements for Increasing the Levothyroxine Dose During Pregnancy in Women with Primary Hypothyroidism."
Background: Most women with hypothyroidism require an increase in their dose of levothyroxine (LT4) after conception. To minimize fetal and maternal complications of maternal hypothyroidism, it is thought that women should be rapidly restored to the euthyroid state. The objectives of this study was to determine the percentage of hypothyroid women who would need to increase their dose of LT4 dose even if they had a preconception (pre-C) serum thyrotropin (TSH) of <2.5 mIU/L as recommended by the Endocrine Society's guidelines and to ascertain whether there was a relationship between the pre-C TSH value and the need to increase the LT4 dose during pregnancy. Methods: Fifty-three pregnant women with hypothyroidism on LT4 treatment in whom the pre-C serum TSH was <2.5 mIU/L, but which was within the normal range, within the 6 months before pregnancy were retrospectively studied. An additional selection criterion was that their LT4 dose at the time of their first prenatal visit was the same as that received pre-C. Results: Seventeen patients had to increase their LT4 dose during pregnancy, because their serum TSH was increased at the time of the first prenatal visit (Group 1); and 36 patients did not have to increase their dose of LT4 during pregnancy (Group 2). The pre-C TSH was significantly higher in Group 1 (1.55 ± 0.62 mIU/L) than in Group 2 (0.98 ± 0.67 mIU/L). When pre-C TSH range was 1.2-2.4 mIU/L, 50% of the patients required an increase in the LT4 dose during pregnancy. In contrast, when the pre-C TSH was <1.2 mIU/L, only 17.2% (p < 0.02) had to increase the LT4 dose during pregnancy. Conclusions: We suggest that in women with hypothyroidism who are planning to become pregnant, serum TSH levels should be in the normal range but should not be greater than about 1.2 mIU/mL.
1 Endocrinology Division, Durand Hospital , Buenos Aires, Argentina .
This article was published in the following journal.
Name: Thyroid : official journal of the American Thyroid Association
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/20860419
- DOI: http://dx.doi.org/10.1089/thy.2009.0457
Medical and Biotech [MESH] Definitions
Dose-response Relationship, Radiation
The relationship between the dose of administered radiation and the response of the organism or tissue to the radiation.
Dose-response Relationship, Drug
The relationship between the dose of an administered drug and the response of the organism to the drug.
Dose-response Relationship, Immunologic
A specific immune response elicited by a specific dose of an immunologically active substance or cell in an organism, tissue, or cell.
Damages to reproductive health prior to conception (FERTILIZATION), a legal term for torts liability concerning environmental safety issues. Preconception injuries may involve either the male or the female, such as chromosomal mutations in the OVA or the SPERMATOZOA.
Lethal Dose 50
The dose amount of poisonous or toxic substance or dose of ionizing radiation required to kill 50% of the tested population.
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