Eduardo Gaitan

Epidemiology of iodine deficiency.

Iodine deficiency (ID) causes goiter, cretinism, neonatal hypothyroidism, irreversible mental retardation, and child and infant death. Over one billion people are at risk, most of them in developing countries. While ID is the primordial factor in these conditions, other environmental and host factors significantly modify the magnitude and clinical presentation of iodine deficiency disorders. The interactions and mechanisms by which these factors operate are complex and mostly unknown, requiring more investigation.

Humic substances, a possible source of environmental goitrogens

Abstract The by-products of humic substances (HS), resorcinol, orcinol, phloroglucinol, pyrogallol, 3,4- and 3,5-dihydroxybenzoic acids, and ortho - and meta -phthalic acids, have been tested for antithyroid and goitrogenic activities. By two in vitro assays all compounds, except the phthalic acids, were potent inhibitors of the thyroid peroxidase enzyme, and of thyroidal 125 I uptake and/or its incorporation into thyroid hormones using thyroid slices. Resorcinol in drinking water was goitrogenic as indicated by in vivo assay in rats. These findings, the identification of resorcinol in the water supply of an endemic goiter district in western Colombia, where increased goiter prevalence is associated with watersheds rich in organic matter, and results of elemental analysis of goitrogenic water extracts from the same district showing a composition similar to that of aquatic HS, suggest that HS degradation by-products may play an important role in the etiology of endemic goiter.

Antithyroid effects of coal‐derived pollutants

Endemic goiter in iodide-sufficient areas of the United States and Colombia has been linked to watersheds rich in coal and shale, which several reports suggest are the source of water-borne goitrogens. In this report the potential antithyroid activities of aqueous coal and shale extracts and of compounds identified in aqueous effluents from coal conversion processes were assayed in thyroid peroxidase (TPO) and thyroid slice systems. Aqueous extracts of coal and black shale were potent inhibitors of TPO or 125I organification by thyroid slices. The most abundant water-soluble compounds derived from coal are dihydroxy-phenols, thiocyanate, disulfides, and hydroxypyridines. The dihydroxyphenols resorcinol, 2-methylresorcinol, and 5-methylresorcinol (orcinol) were 26.7, 22.5, and 7.2 times more potent, respectively, than the antithyroid drug 6-propylthiouracil (PTU). Other dihydroxyphenols and thiocyanate were less potent but comparable in activity to PTU. All dihydroxypyridines and 3-hydroxypyridine produced inhibitory effects comparable to PTU. None of the disulfides inhibited TPO. The antiperoxidase effects of combinations of two dihydroxyphenols or one dihydroxyphenol and SCN were additive, whereas the effects of a combination of four dihydroxyphenols at threshold inhibitory concentrations were synergistic, resulting in net effects equivalent to or greater than the sum of the individual effects. Thus, antithyroid effects may be greatly amplified by exposure to multiple coal-derived goitrogens and could be many times that produced by any one of the contributing pollutants. These results demonstrate that potent water-borne goitrogens are derived from coal and shale and that their contamination of water supplies could pose a serious threat of thyroid disorders.

Iodine-Sufficient Goiter and Autoimmune Thyroiditis: The Kentucky and Colombian Experience

Thyroid disorders constitute today a significant public health problem in Colombia, S.A. and in the United States (1,2). Goiter continues to occur in some areas despite adequate iodine supplementation. For instance, a continued high prevalence of goiter in many localities of western Colombia, as well as in the coal-rich Appalachian area of eastern Kentucky, has been reported (1,2). The incidence of lymphocytic autoimmune thyroiditis (AT) has has steadily increased in the U.S. during the past five decades and it has been attributed to iodine prophylaxis and excessive iodine intake (2). In western Colombia, S.A., where iodine prophylaxis was instituted thirty years ago, a similar trend has been documented (3). However, lymphocytic infiltration was of high degree in most of the U.S. glands, while it was minimal in 70% of the Colombian cases. Thus, recent studies were designed to reassess and gain insight into the problem of goiter and AT in areas of eastern Kentucky and western Colombia, where goiter persists despite iodine supplementation. Nearby localities where goiter has not been a problem were similarly investigated.