Geologically induced goiters.

Geologically induced goiters

Worldwide, an estimated 400 million people suffer from goiter, or enlarged thyroid glands--a condition that can, if left untreated, lead to reduced thyroid function. While the majority of goiters can still be traced to insufficient dietary iodine, roughly 25 percent cannot. Many of the 100 million persons who fall into this latter category may be victims of goiter-producing geological factors, according to Eduardo Gaitan, chief of endocrinology at the University of Mississippi School of Medicine in Jackson. Studies that he and his collaborators from a number of institutions have conducted in Colombia and the United States now indicate that natural environmental pollutants in drinking water appear capable of inducing goiter and interfering with thyroid function.

For example, in some Appalachian coal-mining regions of Kentucky, despite adequate iodine, "as many as 37 percent of the children have enlarged thyroid glands,' Gaitan says. (Children are more susceptible to goiter, he notes, and if untreated can suffer physical and mental development problems.) Their studies in these regions over the past four years now show that resorcinol, a known thyroid inhibitor, is in much of the well water serving the area. "We also found other compounds in the water--phthalates--which under the action of bacteria can be transformed into dihydroxy benzoic acids,' Gaitan says. Research by his team has shown that these can also interfere with thyroid function. Recently, they found both compounds in the drinking water serving high-goiter areas in Colombia.

Resorcinol and dihydroxy benzoic acids are among coal-processing wastes, their work shows. Gaitan says it thus appears "the geological composition' of the Kentucky and Colombian areas--especially limestone rich in organic compounds such as coal--may be contributing these compounds.

While many goiter symptoms affecting the Colombian and Kentucky populations they study are similar, all of their contributing sources may not be. In two high-goiter counties of Kentucky, Gaitan's group found that a third of affected children "make antibodies against their own thyroid glands'--a condition known as autoimmune thyroiditis. No similar antibodies were identified in any of the Colombians studied. Moreover, Gaitan points out, two chemicals isolated from the Kentucky water--methoxy anthracene and bromoform--are not found in the Colombian water. Studies conducted by other researchers have shown that buffalo rats fed these two compounds will develop autoimmune thyroiditis, Gaitan says.