Persistence of goitre in children post-salt iodization in Islamic Republic of Iran: autoimmune status

We evaluated the prevalence of autoimmune thyroiditis in a random sample of 1188 schoolchildren aged 8-13 years with normalized iodine intake in the Islamic Republic of Iran. The prevalence of goitre was 39.6%; the majority had palpable but non-visible goitre. Of a subsample of 500 children, median urinary iodine excretion [18/8 microg/dL] indicated normal iodine intake. Thyroid peroxidase [TPO] antibody was positive in 3.7% of children and was significantly correlated with the prevalence of goitre and hypothyroidism. No correlation was seen between urinary iodine excretion and positive TPO antibody, mean TPO antibody, hypothyroidism or prevalence of goitre. Autoimmune thyroiditis explains some cases of goitre but other goitrogenic factors need to be evaluated

[Prevalence of autoimmune thyroiditis in school children 10 years after normalized iodine intake]

Iodine deficiency has been identified as a significant public health problem in Iran. The main strategy for control of iodine deficiency was country wide salt iodination. 10 years after starting this program, goiter is still endemic in some school children. The most important differential diagnosis is autoimmune thyroiditis. The aim of the present study was to evaluate prevalence of autoimmune thyroiditis in school children with normalized iodine intake. 1188 school children, aged 8-13 years, were selected by cluster random sampling to evaluate prevalence of goiter. From a total of 1188, 500 school children were chosen to assess urinary iodine excretion, free T4, free T3, TPO anti body [TPOAb] and TSH. Goiter was endemic in 39.6%[95% CI 36/3%-41/7%] but majority of them had grade I thyromegaly. Median urinary iodine excretion [18/8 microg/ dl] indicated normal iodine intake. Mean [95%CI] free T4, free T3 and TSH concentration were 13.1[12.8-13.3] pg/ml, 3.7[3.6-3.8]pg/ml and 2.5 [2.2-2.8] IU/ml respectively. TPOAb was positive in 3.7% of children with a higher prevalence in girls[P< 0.001]. The prevalence of hypothyroidism and hyperthyroidism was 9% and 0.2% respectively but only 0.8% of school children had TSH>10. There was a significant relationship between detection of positive TPOAb, prevalence of goiter and hypothyroidism; however no relation was seen between urinary iodine excretion status and detection of positive TPOAb, hypothyroidism and prevalence of goiter. Despite median urinary iodine excretion being normal, persistence of goiter suggested presence of goiterous factors; alhought the autoimmune mechanisms of thyroid may to some extent autoimmune of thyroid explain some part of the goiter prevalence it is however necessary to evaluate other factors

[Prevalence of goiter and iodine deficiency ten years after salt iodinezation in school children [8-13 years old] in Marvdasht]

Iodine deficiency was endemic in Pars province since several years. Mandatory production of iodinized salt for household use was started from 1994. The aim of this study was to evaluate the prevalence of goiter, urinary iodine excretion in school children ten years after starting the program. A cross sectional study in which 1188 school children, aged of 8 - 13 years, from Marvdasht city were chosen by random cluster sampling for evaluation of goiter prevalence according to WHO classification. Of these this 1188 school children, 500 persons were selected for evaluation of urinary iodine excretion [UIE] by digestion method, difference in UIE was assessed among different age groups, goitrous and non goitrous school children. Following the assessment, goiter was found to be still endemic in school children [39.6%] but majority of them had gradel goiter. Median urinary iodine [95% Cl] excretion levels in boys and girls and total number of school children were 17 micro g/dl [13.1-20.9], 22.4 micro g/dl [20.4-24.1] and 18.8 micro g/dl [16.1-21.5] respectively. Differences in UIE between two sexes were significant [P < 0.001] but differences among age groups were not significant. The UIE levels in goitrous and non goitrous school children were 18 micro g/dl [16.4-19.9] and 20 micro g/dl [17.1-22.9] respectively, with no statistically significant difference. Prevalences of school children with urinary excretion in normal, above normal and below normal ranges were 29.5%, 47.5%, 23% respectively, meanwhile less than 13% had urinary iodine excretion < 5 micro g/dl. We conclude that the iodine intake is sufficient but persistent, albeit, reduced prevalence of goiter in spite of adequate iodine supplementation suggests the existence of additional causes in goiterogenesis. It is necessary to consider the role of other factors in persistence of goiter