1Pediatrics, Gynecology & Obstetrics Unit, Riotinto Hospital, Spain
2Endocrine, Thyroid & Obesity Research Group. Germans Trias i Pujol Research Institute, Spain
3Pediatrics, Gynecology & Obstetrics Department, Autonomous University of Barcelona, Spain
4Endocrinology & Nutrition Department, Germans Trias i Pujol University Hospital, Spain
5Gynecology & Obstetrics Department, Germans Trias i Pujol University Hospital, Spain
6Pediatrics Department, Germans Trias i Pujol University Hospital, Spain
7Clinical Biochemistry Department, Germans Trias i Pujol University Hospital, Spain
8Department of Gastroenterology, Virgen de la Victoria University Hospital, Spain
**Both authors contributed equally to this manuscript as co-first authors.
Inés Velasco, Pediatrics, Endocrine, Gynecology & Obstetrics Unit, Riotinto Hospital, Thyroid & Obesity
Research Group, Gynecology & Obstetrics Department, Germans Trias i Pujol Research Institute, Autonomous University of Barcelona,
Prof Manel Puig Domingo, MD, PhD, Endocrinology & Nutrition Department, Germans Trias i Pujol University Hospital, and Germans
Trias i Pujol Research Institute, Camí de les escoles, carretera de Can Ruti s/n 08916 Badalona, Spain. Tel: ;
Received: August 17, 2020; Published: September 03, 2020
Introduction: It remains unclear to what extent intrinsic maternal characteristics, lifestyle or diet and dietary supplements
contribute to explain the variability of maternal thyroid function. The aim of this study was to analyse the effect of age, parity,
pregestational body mass index (BMI), beta human chorionic gonadotropin (β-hCG), thyroid autoantibodies, smoking habit and use
of vitamins/supplements on maternal thyroid function variability throughout pregnancy.
Methods: A prospective, observational study was carried out including 339 healthy pregnant women from their first to their third
trimester. Clinical and biological variables were registered at each stage. Univariate correlation and multiple linear regression
analysis for thyroid parameters were performed in the three trimesters.
Results: Thyrotropin (TSH) in the first trimester (1T) was dependent on free thyroxine (FT4), maternal age, β-hCG and
smoking habit. FT4 levels in the 1T were significantly lower in obese women (0.937±0.078ng/dl), compared with overweighed
(0.981±0.14ng/dl) and normal weight women (0.989± 0.98ng/dl) (p=0.012). Multiple linear regression showed that FT4 in all
trimesters is significantly dependent on pregestational BMI. Additionally, TSH and FT4 in the 1T were significantly related to TSH
and FT4 levels in second and third trimesters, respectively. All studied factors influenced TSH with different degree all-over the
pregnancy. Dietary supplements did not modify maternal thyroid function.
Conclusion: FT4 availability during the first half of the gestation can be hindered by maternal overweight/obesity. Beside age,
obesity and smoking, TSH and FT4 in the 1T are very important regarding thyroid function variability in further stages of the