TSH levels and risk of miscarriage in women on long-term levothyroxine: a community-based study

Taylor, Peter ORCID: https://orcid.org/0000-0002-3436-422X, Minassian, Caroline, Rehman, Anis, Iqbal, Ahmed, Draman, Mohd Shazli, Hamilton, William, Dunlop, Diana, Robinson, Anthony, Vaidya, Bijay, Lazarus, John, Thomas, Sara, Dayan, Colin ORCID: https://orcid.org/0000-0002-6557-3462 and Okosieme, Onyebuchi 2014. TSH levels and risk of miscarriage in women on long-term levothyroxine: a community-based study. Journal of Clinical Endocrinology & Metabolism 99 (10) , pp. 3895-3902. 10.1210/jc.2014-1954

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Abstract

Context: Thyroid dysfunction is associated with adverse obstetric outcomes, but there is limited information on pregnancy outcomes in women established on levothyroxine. Objective: The objective of the study was to determine the relationship between TSH levels and pregnancy outcomes in levothyroxine-treated women in a large community-based database. Design: This was a historical cohort analysis. Patients: Individuals with a first prescription of levothyroxine from 2001 through 2009 (n = 55 501) were identified from the UK General Practice Research Database (population 5 million). Of these, we identified 7978 women of child-bearing age (18–45 y) and 1013 pregnancies in which levothyroxine had been initiated at least 6 months before conception. Main Outcome Measures: TSH, miscarriage/delivery status, and obstetric outcomes were measured. Results: Forty-six percent of levothyroxine-treated women aged 18–45 years had a TSH level greater than 2.5mU/L (recommended upper level in the first trimester). Among pregnant women who had their TSH measured in the first trimester, 62.8% had a TSH level greater than 2.5 mU/L, with 7.4% greater than 10 mU/L. Women with TSH greater than 2.5 mU/L in the first trimester had an increased risk of miscarriage compared with women with TSH 0.2–2.5 mU/L after adjusting for age, year of pregnancy, diabetes, and social class (P = .008). The risk of miscarriage was increased in women with TSH 4.51–10 mU/L [odds ratio (OR) 1.80, 95% confidence interval (CI) 1.03, 3.14)] and TSH greater than 10 mU/L (OR 3.95, 95% CI 1.87, 8.37) but not with TSH 2.51–4.5 mU/L (OR 1.09, 95% CI 0.61, 1.93). Conclusions: The majority of levothyroxine-treated women have early gestational TSH levels above the recommended targets (>2.5 mU/L) with a strong risk of miscarriage at levels exceeding 4.5 mU/L. There is an urgent need to improve the adequacy of thyroid hormone replacement in early pregnancy.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Medicine Systems Immunity Research Institute (SIURI)
Subjects:	R Medicine > R Medicine (General)
Publisher:	The Endocrine Society
ISSN:	0021-972X
Date of Acceptance:	17 June 2014
Last Modified:	31 Oct 2022 08:56
URI:	https://orca.cardiff.ac.uk/id/eprint/79272

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