Iodine status as determined by urinary iodine excretion in Lesotho two years after introducing legislation on universal salt iodization

Abstract 

Objective

Mild to severe iodine deficiency has been documented in Lesotho since 1960. To eliminate the persisting iodine deficiency, legislation on universal salt iodization was introduced in 2000 as a long-term public health intervention strategy. We assessed the urinary iodine status of school children and women of child-bearing age in Lesotho 2 y after the introduction of legislation on universal salt iodization.

Methods

A 31-cluster national survey was conducted in 2002 by using the proportion to population size method. In each cluster, 30 women ages 15 to 30 y and 30 primary school children ages 8 to 12 y were randomly selected to provide urine samples for urinary iodine analysis. Data were interpreted according to criteria of the World Health Organization, United Nations Children's Fund, and International Council for Control of Iodine Deficiency Disorders (2001). Statistical analysis was performed using SAS.

Results

We analyzed 912 urine samples from children and 924 from women. The median urinary iodine concentrations were 214.7 μg/L for children and 280.1 μg/L for women, indicating more than adequate iodine intake. Median iodine concentration was higher in the lowlands (256.0 μg/L in children and 329.9 μg/L in women) than in the mountains (99.30 μg/L in children and 182.6 μg/L in women). Analysis of the distribution of the data showed values below 50 μg/L in 10.1% of children and in 9.8% of women. In addition, 21.5% of children and 17.9% of women had urinary iodine excretion values below 100 μg/L. In contrast, 36% of children and 47.2% of women had urinary iodine concentrations in excess of 300 μg/L.

Conclusion

Results of urinary iodine excretion measurements indicated that iodine deficiency has been eliminated as a public health problem in Lesotho. However, the high median urinary iodine concentration of women in the lowlands indicated the possibility of a risk of iodine-induced hyperthyroidism in vulnerable people.

Keywords: Urinary iodine, Women, School children, Population survey, Lesotho