Overweight increases risk of first trimester hypothyroxinaemia in iodine-deficient pregnant women.
Hypothyroxinaemia early in pregnancy may impair fetal brain development. Increased body weight has been associated with low thyroxine concentrations in non-pregnant women. In pregnant women, morbid maternal obesity is a risk factor for thyroid dysfunction. But whether lesser degrees of overweight that are much more common could be a risk factor for hypothyroxinaemia in pregnancy is unclear. The objective of this study was to investigate if overweight increases risk for thyroid dysfunction, and specifically hypothyroxinaemia, in iodine-deficient pregnant women. We performed a cross-sectional study at first hospital visit among healthy Thai pregnant women. We measured weight and height, urinary iodine concentration (UIC), serum thyroid hormones and thyroglobulin. Pre-pregnancy weight and relevant dietary factors were determined by questionnaire, and body mass index (BMI) was used to classify weight status. Among 514 women (mean gestational age, 11 weeks) with a median UIC of 111 μg dL(-1) , indicating mild iodine deficiency, 12% had low free thyroxine (fT4) concentrations: 3% had overt hypothyroidism; 7% had subclinical hypothyroidism; and 8% had isolated hypothyroxinaemia. Based on pre-pregnancy BMI, 26% of women were overweight or obese. In a multiple regression model, BMI was a negative predictor of fT4 (β = -0.20, P < 0.001). Compared to normal weight women, the prevalence ratio (95% CI) of a low fT4 in overweight women was 3.64 (2.08-6.37) (P < 0.01). Iodine-deficient pregnant Thai women who are overweight have a 3.6-fold higher risk of hypothyroxinaemia in the first trimester compared to normal weight women. Targeted screening should consider overweight a potential risk factor for thyroid dysfunction in pregnant women in iodine-deficient areas.
Division of Human Nutrition, Wageningen University, Wageningen, the Netherlands; Institute of Nutrition, Mahidol University, Nakhon Pathom, Thailand.
Sueppong
S
Gowachirapant
Alida
A
Melse-Boonstra
Pattanee
P
Winichagoon
Michael B
MB
Zimmermann
D000293:Adolescent; D000328:Adult; D044466:Asian People; D015992:Body Mass Index; D001835:Body Weight; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood* / Q000453:epidemiology* / Q000209:etiology; D007455:Iodine / Q000097:blood / Q000172:deficiency*; D050177:Overweight / Q000097:blood* / Q000150:complications; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D015995:Prevalence; D012307:Risk Factors; D013785:Thailand / Q000453:epidemiology; D013954:Thyroglobulin / Q000097:blood; D013960:Thyroid Function Tests; D013974:Thyroxine / Q000097:blood; D055815:Young Adult
D013954:Thyroglobulin; D007455:Iodine; D013974:Thyroxine
hypothyroxinaemia; iodine deficiency; obesity; overweight; pregnant women; thyroid dysfunction