ANTITHYROID AND GOITROGENIC EFFECTS OF COAL-WATER EXTRACTS FROM IODINE-SUFFICIENT GOITER AREAS

Goiter in iodine-sufficient areas has been linked to water-borne goitr ogens in watersheds and aquifers rich in coal and shale. In the presen t study, the potential antithyroid and goitrogenic effects of coal-wat er extracts (CWE) were investigated in vivo in rats after chronic and acute oral administration of CWE, and in vitro by a thyroid peroxidase (TPO) enzyme system. CWE was prepared by continuous extraction of gro und (40 mesh) Appalachian coal with goitrogen-free water (GFW). Female Buffalo rats fed on Purina iodine-rich diet (12 mug I-/day/rat), were given ad lib CWE (50 mg/ml; approximately 20 mL/day/rat) or GFW (cont rols) for 2 months. At the end of the experiment, I-125 1 muCi, was in jected i.p. and 4 h later the thyroid glands were removed, weighed, an d analyzed histologically and for total I-125 and I-125-labeled compou nds. Rats on CWE had larger thyroid glands [7.2 +/- 0.3 mg/100 g (mean +/- SE) vs 5.0 +/- 0.5 controls; p < 0.005] with distinct histologica l changes of smaller thyroid follicles, some with columnar epithelium, and with more dense colloid than in controls, and had significant inh ibition of the coupling mechanism for production of thyroid hormones [ 125MIT + DIT/125T3 + T4: 5.1 +/- 0.2 vs 3.9 +/- 0.1 controls, p < 0.00 5; and 125T3 + T4 (%): 10.6 +/- 0.3 vs 12.6 +/- 0.4 controls, p < 0.00 51. Female Sprague-Dawley rats under the same conditions as Buffalo ra ts were given acutely by GI tube 2 mL of CWE (5 g/mL) or GFW (controls ). Rats on CWE suppressed thyroid I-125-organification [I-125 (%): 56. 2 +/- 3.5 (mean +/- SE) vs 45.6 +/- 1.7 controls, p < 0.03; 125MIT + D IT (%): 39.3 +/- 3.9 vs 50.5 +/- 1.5 controls, p < 0.03; and I-125/125 MIT + DIT: 1.6 +/- 0.3 vs 0.9 +/- 0.06 controls, 0.05 > p < 0.101. Aqu eous extracts of 25 and 100 mg of coal produced 24.3 +/- 2.1% (mean +/ - SE) (p < 0.05) and 54.6 +/- 6.3% (p < 0.01) inhibition, respectively , of TPO. These data provide direct experimental evidence that water-b orne antithyroid and goitrogenic compounds are derived from coal, and are consistent with epidemiological observations of higher goiter prev alence in iodine-sufficient coal-rich areas than in areas devoid of or ganic rocks. Their contamination of water supplies could pose a seriou s threat of thyroid disorders.