Impact of selective iron and/or iodine interventions on iron and iodine status of adolescents

The impact of iron and iodised salt supplementation and iron with iodised salt supplementation for a period of six months was studied in relation to non-supplemented controls, on selected indicators of iron and iodine status among goitrous and non goitrous adolescents. A significant reduction in total goitre rate (TGR) and visible goitre rate (VGR) was observed in the group given iodised salt alone or with iron supplements. No change was observed in TGR in the group receiving iron supplements though VGR decreased. An increase in urinary iodine excretion (UIE) was observed among goitrous and non goitrous subjects receiving iodised salt alone or iron supplements alone. The goitrous control subjects in contrast showed a significant decrease in their UIE (-10.9 mcg/dL p < 0.05). Iodised salt supplementation caused an increase in T4 (thyroxine) in goitrous and non goitrous subjects and a decrease in TSH (thyroid stimulating hormone) in goitrous subjects. However, iron supplementation had an adverse effect on T3 (triidothyronine) and T4 in non goitrous subjects. Dual supplementation caused a significant decline in T3 (among goitrous subjects) and T4 concentrations (among non goitrous subjects). Haemoglobin (Hb) and serum ferritin (sf) concentrations improved with iodised salt among both the goitrous and non goitrous subjects, but for goitrous subjects, not with iron alone. This study suggests that if a subject is both iron and iodine deficient, iodine deficiency may be corrected in part by iron or iodine supplementation, although their co-administration may not be synergistic. The metabolic relationship between iron and iodine deficiency needs further investigation. However, goitre prevalence is clearly ameliorated with combined micronutrient supplementation to a greater extent than with iodised salt alone and not at all with iron alone.

Iodine status in pregnancy

The iodine status of 429 pregnant women in different trimesters from the lower socio-economic strata of the urban slums of Bombay was assessed using clinical and biochemical parameters. The total goitre rate (TGR) of 45% and a visible goitre rate (VGR) of 3.04% was observed. There was an evident increase in the TGR during the months of pregnancy. The urinary iodine excretion pattern revealed mild iodine deficiency. 55% of the women had urinary iodine excretion less than 5 mcg/dl with 13.2% having less than 2 mcg/dl. Elevated T3 and T4 levels were observed in 64 and 40% respectively of the women surveyed, while only 1.8% of them had TSH levels higher than the normal range. No significant difference in the levels of thyroid hormone (T3 or T4) was noted between the euthyroid and goitrous subjects. The mean TSH levels in euthyroid women were however significantly higher than those with signs of goitre.

Iodine deficiency in adolescents from Bombay slums

BACKGROUND

Iodine deficiency may be associated with endemic goitre, lowered levels of circulating thyroid hormone and suboptimal brain function. We studied iodine deficiency, thyroid status and scholastic performance in 866 (416 girls and 450 boys) adolescents from the slums of Bombay.

METHODS

We examined 866 adolescents (416 girls and 450 boys) to determine the presence of goitre. Circulating levels of T3 and T4 were estimated by radioimmunoassay and of thyroid stimulating hormone by the immunoradiometric assay technique. Their scholastic performance was assessed by the average marks obtained in the last examination.

RESULTS

The prevalence of goitre was 56% in both boys and girls. The visible goitre rate was also similar in boys (9.8%) and girls (10.6%). We found no significant difference in the mean urinary iodine excretion and urinary iodine to creatinine ratio between boys and girls, but the mean serum T3 and T4 levels were lower in girls than in boys, while the thyroid stimulating hormone levels were higher. The mean thyroid hormone levels were consistent with normal thyroid function. With an increase in the size of goitre, there was a decrease in urinary iodine excretion, urinary iodine to creatinine ratio, T3 and T4 levels while the thyroid stimulating hormone levels increased. The scholastic performance of the adolescents with goitre was poor. Forty-eight per cent of them obtained less than 50% marks and their academic grades showed a significant association with thyroid stimulating hormone levels.

CONCLUSION

Goitre has a high prevalence among adolescents in the slums of Bombay. This can be attributed partly to the increasing demand for iodine at puberty which cannot be satisfied with the limited amounts available in food. The children also show a poor scholastic performance. Mild iodine deficiency can be easily controlled by encouraging the use of iodized salt in adolescents.

Prevalence of iodine deficiency disorders in adolescents

In the present study the iodine status of 300 adolescent boys and girls was assessed by clinical examination and biochemical tests. The clinical examination revealed the total goitre rate (TGR) to be 65.2% among boys, and 69.6% among girls. The visible goitre rate (VGR) was 17.7% among boys and 21.1% among girls. Nutritional status of all adolescents was found to be poor as compared to their well-nourished counterparts. Using discriminant analysis it was found that age, height and weight of the adolescents were significantly related to goitre grade (p < 0.001), and they are important in prediction of goitre. Mild and moderate iodine deficiency were found to be prevalent among the adolescents. On the basis of urinary iodine/creatinine ratio, 38% of the adolescents were found to be suffering from mild iodine deficiency, i.e. average urinary iodine excretion between 50-100 mcg iodine/g creatinine. Moderate iodine deficiency (< 50 mcg iodine/g creatinine) was found to be prevalent among 12.4% of the adolescents. The results of this study indicate a high prevalence of mild and moderate IDD among the adolescents studied.