Authors : Jaiswal N, Melse A, Thomas T, Basavaraj C, Sharma SK, Srinivasan K, Zimmermann M
Publication Year : 2014
BACKGROUND:
Iodine requirements are increased during pregnancy to maintain maternal and fetal euthyroidism. There have been recent improvements in iodized salt coverage in India but whether iodized salt is enough to sustain iodine requirements during pregnancy providing adequate iodine to pregnant women remains uncertain. Our aims were to measure thyroid status in first trimester pregnant women in southern India and assess potential determinants of thyroid function, including iodine status, thyroid autoimmunity, dietary patterns, body weight and anemia.
METHODS:
Cross-sectional study among 334 pregnant women ≤14 weeks of gestation, in Bangalore, India. We measured anthropometrics, urinary iodine concentration (UIC), maternal thyroid volume (by ultrasound) and thyroid function. We applied a TSH upper limit of 2.5 mIU/L to classify thyroid insufficiency. Using a questionnaire, we obtained socio-demographic and dietary data, obstetric history, and use of iodised salt and iodine supplements.
RESULTS:
Among the women, mean (SD) gestational age was 10.3 (2.5) weeks, 67% were nulliparous, 21% were vegetarian, 19% were anemic and 23% were overweight or obese. Iodized salt was used by 98% of women and they were iodine sufficient: median UIC (range) was 184.2 (8.1-1152) µg/L median (range) UIC was 184 (97, 349) µg/L and all had normal thyroid volume. However, 18% of women had thyroid insufficiency: 3.7% had overt hypothyroidism (83% with positive TPO-Ab), 9.2% had subclinical hypothyroidism and 5.2% had hypothyroxinemia. Women consuming vegetarian diets did not have significantly lower iodine intakes or higher risk of hypothyroidism than those consuming mixed diets, but overweight/obesity and anemia predicted thyroid insufficiency.
CONCLUSION:
In this urban population of southern India, pregnant women have adequate iodine status in the first trimester. Despite this, many have thyroid insufficiency, and the prevalence of overt hypothyroidism is >5-fold higher than reported in other iodine-sufficient populations of pregnant women.