Effects of Levothyroxine Therapy on Pregnancy Outcomes in Women with Subclinical Hypothyroidism.
Subclinical hypothyroidism (SCH) has been associated with increased risk of adverse pregnancy outcomes in some, but not all, studies. Uncertainty remains regarding the impact of levothyroxine (LT4) therapy on improving health outcomes in pregnant women with SCH. The objective of this study was to assess the potential benefits of LT4 therapy in pregnant women with SCH.



The medical records were reviewed of pregnant women with SCH, defined as an elevated serum thyrotropin (TSH) of >2.5 mIU/L for the 1st trimester or >3 mIU/L for the 2nd and 3rd trimesters, but ≤10 mIU/L. Pregnant women were divided into two groups depending on whether they received LT4 (group A) or not (group B). Pregnancy loss and other pre-specified adverse outcomes were evaluated during follow-up.



There were 82 women in group A and 284 in group B. Group A had a higher body mass index (p = 0.04) and a higher serum TSH level (p < 0.0001) compared with group B. Group A had fewer pregnancies lost (n = 5 [6.1%] vs. n = 25 [8.8%]; p = 0.12), low birth weight (LBW) offspring (1.3% vs. 10%; p < 0.001), and no neonates with a five-minute Apgar score ≤7 (0% vs. 7%; p < 0.001) compared with group B. Other pregnancy-related adverse outcomes were similar between the two groups. Inferences remained unchanged after considering different models to adjust for potential predictors of outcome.



LT4 therapy is associated with a decreased risk of LBW and a low Apgar score among women with SCH. This association awaits confirmation in randomized trials before the widespread use of LT4 therapy in pregnant women with SCH.
1 Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic , Rochester, Minnesota.|2 Knowledge and Evaluation Research Unit (KER-Endo), Mayo Clinic , Rochester, Minnesota.
Spyridoula
S
Maraka
1 Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic , Rochester, Minnesota.|2 Knowledge and Evaluation Research Unit (KER-Endo), Mayo Clinic , Rochester, Minnesota.
Naykky M
NM
Singh Ospina
1 Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic , Rochester, Minnesota.|3 Division of Endocrinology, Department of Medicine, National University of Ireland , Galway, Ireland .
Derek T
DT
O'Keeffe
1 Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic , Rochester, Minnesota.|2 Knowledge and Evaluation Research Unit (KER-Endo), Mayo Clinic , Rochester, Minnesota.|4 Division of Endocrinology, Department of Internal Medicine, University Hospital "Dr. Jose E. Gonzalez," Autonomous University of Nuevo Leon , Monterrey, Mexico .
Rene
R
Rodriguez-Gutierrez
1 Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic , Rochester, Minnesota.
Ana E
AE
Espinosa De Ycaza
5 Department of Pediatric and Adolescent Medicine, Mayo Clinic , Rochester, Minnesota.
Chung-Il
CI
Wi
5 Department of Pediatric and Adolescent Medicine, Mayo Clinic , Rochester, Minnesota.
Young J
YJ
Juhn
6 Department of Obstetrics and Gynecology, Mayo Clinic , Rochester, Minnesota.
Charles C
CC
Coddington
1 Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic , Rochester, Minnesota.|2 Knowledge and Evaluation Research Unit (KER-Endo), Mayo Clinic , Rochester, Minnesota.
Victor M
VM
Montori
1 Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic , Rochester, Minnesota.
Marius N
MN
Stan
D000022:Abortion, Spontaneous / Q000453:epidemiology*; D000328:Adult; D001034:Apgar Score; D058070:Asymptomatic Diseases; D016022:Case-Control Studies; D016640:Diabetes, Gestational / Q000453:epidemiology*; D005260:Female; D005317:Fetal Growth Retardation / Q000453:epidemiology*; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000188:drug therapy*; D007230:Infant, Low Birth Weight; D007363:Intensive Care Units, Neonatal / Q000706:statistics & numerical data; D011225:Pre-Eclampsia / Q000453:epidemiology*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood / Q000188:drug therapy*; D011256:Pregnancy Outcome / Q000453:epidemiology; D047928:Premature Birth / Q000453:epidemiology*; D012189:Retrospective Studies; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000627:therapeutic use*
D013972:Thyrotropin; D013974:Thyroxine