Benefits and risks from the national strategy for improvement of iodine nutrition in Bulgaria: study on schoolchildren living in a rural area

Iodine excess as an environmental risk factor for autoimmune thyroid disease

The global effort to prevent iodine deficiency disorders through iodine supplementation, such as universal salt iodization, has achieved impressive progress during the last few decades. However, iodine excess, due to extensive environmental iodine exposure in addition to poor monitoring, is currently a more frequent occurrence than iodine deficiency. Iodine excess is a precipitating environmental factor in the development of autoimmune thyroid disease. Excessive amounts of iodide have been linked to the development of autoimmune thyroiditis in humans and animals, while intrathyroidal depletion of iodine prevents disease in animal strains susceptible to severe thyroiditis. Although the mechanisms by which iodide induces thyroiditis are still unclear, several mechanisms have been proposed: (1) excess iodine induces the production of cytokines and chemokines that can recruit immunocompetent cells to the thyroid; (2) processing excess iodine in thyroid epithelial cells may result in elevated levels of oxidative stress, leading to harmful lipid oxidation and thyroid tissue injuries; and (3) iodine incorporation in the protein chain of thyroglobulin may augment the antigenicity of this molecule. This review will summarize the current knowledge regarding excess iodide as an environmental toxicant and relate it to the development of autoimmune thyroid disease.

Male gender differences in the thyroid ultrasound features, thyroid peroxidase antibodies and thyroid hormone levels: a large population-based study

Anti-thyroid antibodies and thyroid ultrasound (US) are currently the methods for diagnosing autoimmune thyroid disease. Few data exist on their utility in males. The aim of the study was to investigate the gender-specific relationship between the Anti-TPO levels, thyroid ultrasound features, and thyroid function in a population with no known thyroid disorder.

METHODS

We studied 1,887 subjects, 20-80 years, 953 females, 934 males. Anti-TPO antibodies, TSH and FT4 were measured and ultrasound of the thyroid was performed. The subjects were divided into antibody-positive and antibody-negative, and into four US pattern groups. The prevalence of subclinical (SHT) and overt (OHT) hypothyroidism was determined.

RESULTS

Antibody positivity was found in 23 % of females and 10 % of males (p < 0.01), being highest in the hypoechoic/non-homogenous subgroups [68 % Ab-positive females versus 41 % Ab-positive males (p < 0.001)]. Hypothyroidism was most prevalent in the antibody-positive subjects with hypoechoic non-homogenous pattern (35 %, both genders). Odds ratios for hypothyroidism were similar in males and females with hypoechoic non-homogenous pattern (5.91, 95 %CI 2.50, 13.96 vs. 6.27, 95 % CI 2.64, 14.91), but higher in Ab-positive females than males. SHT was found in 4.5 % of females and 2 % of males, OHT in 3.2 % of females and 1.1 % of males. 65 % of the females with SHT, 81 % of those with OHT, 26 % of the males with SCH and 60 % with OHT were Anti-TPO positive.

CONCLUSION

The prevalence and pattern of autoimmune-related changes differed in the two genders. Hypothyroidism prevalence was similar in both genders when both hypoechoic/non-homogenous pattern and anti-TPO positivity were present.