Iodine status and thyroid function among lactating women in Saharawi refugee camps, Algeria

Abstract

BACKGROUND: Insufficient iodine intake as well as excess iodine intake may cause thyroid diseases. Endemic goitre and high urinary iodine concentration (UIC), probably caused by excess iodine, has been reported among Saharawi refugees. To what extent long-term excess iodine intake have influenced the thyroid function of the refugees is unknown. OBJECTIVE: The main objective was to assess iodine status and thyroid function among lactating women in the Saharawi refugee camps. METHOD: A baseline for a cohort study was performed among 111 lactating Saharawi women (18-50 years) living in the Algerian desert. Samples of casual urine, breast milk, public drinking water, goat - and camel milk were collected for determination of iodine concentrations. Dietary iodine intake through intake of water and milk was registered using 24-h recall. Thyroid function was assessed through serum levels of thyroid stimulating hormone (TSH), thyroglobulin (Tg), tyroxin (T4), thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb). In selected samples triiodothyronine (T3) and thyrotropin receptor antibody (TRAb) were determined. RESULTS: Median UIC was 350 µg/L. The breast milk iodine concentration (BMIC) showed a median concentration of 479 µg/L. Median iodine concentrations in public drinking water, goat - and camel milk was 102, 952 and 2020 µg/L, respectively. The median dietary intake of iodine among the women was 407 µg/day. Thyroid function abnormalities were found in 23.4 % of the women: 12.6 % had subclinical hypothyroidism, 5.4 % autoimmune thyroiditis, 5.4 % subclinical hyperthyroidism, 3.6 % clinical hypothyroidism and 0.9 % clinical hyperthyroidism. Further, 17.1 % of the women had elevated serum Tg levels and positive TgAb was detected in 14.4 %. The age distribution was higher among women with thyroid abnormalities (p = 0.01). Dietary iodine intake correlated well with UIC (rs = 0.24, p = 0.01) and BMIC (rs = 0.47, p < 0.001). The prevalence of thyroid function abnormalities increased with higher UIC, although no significant correlation between UIC and TSH or UIC and Tg was found. CONCLUSION: The lactating women had high levels of iodine in urine and breast milk, probably caused by excessive dietary iodine intake with public drinking water as a major contributor and animal milk presumably increasing the iodine intake when consumed. The high prevalence of thyroid abnormalities indicates that the long-term excess iodine intake might have influenced the thyroid function negatively.