Urinary iodine concentration identifies pregnant women as iodine deficient yet school-aged children as iodine sufficient in rural Niger

Abstract

Objective: To assess iodine status among pregnant women in rural Zinder, Niger and to compare their status with the iodine status of school-aged children from the same households.

Design: Seventy-three villages in the catchment area of sixteen health centres were randomly selected to participate in the cross-sectional survey.

Setting: Salt iodization is mandatory in Niger, requiring 20-60 ppm iodine at the retail level.

Subjects: A spot urine sample was collected from randomly selected pregnant women (n 662) and one school-aged child from the same household (n 373). Urinary iodine concentration (UIC) was assessed as an indicator of iodine status in both groups. Dried blood spots (DBS) were collected from venous blood samples of pregnant women and thyroglobulin (Tg), thyroid-stimulating hormone and total thyroxine were measured. Iodine content of household salt samples (n 108) was assessed by titration.

Results: Median iodine content of salt samples was 5·5 ppm (range 0-41 ppm), 98 % had an iodine content 40 µg/l.

Conclusions: In this region of Niger, most salt is inadequately iodized. UIC in pregnant women indicated iodine deficiency, whereas UIC of school-aged children indicated marginally adequate iodine status. Thus, estimating population iodine status based solely on monitoring of UIC among school-aged children may underestimate the risk of iodine deficiency in pregnant women.

Keywords: Iodine; Niger; Pregnant women; School-aged children; Thyroglobulin; Urinary iodine.

Fig. 1

Flow diagram of clusters and participants through the iodine status assessment of the Niger Maternal Nutrition (NiMaNu) Project (SAC, school-aged child(ren); UIC, urinary iodine concentration)

Fig. 2

Distribution of urinary iodine concentration (UIC) in (a) pregnant women and (b) school-aged children living in the same households in Zinder, rural Niger