Calcium as a Goitrogen*

IN ANCIENT times goiter was thought to be due to the ingestion of some poison in the diet (1), air (2) or water (3), but about a century ago attempts were made to correlate its distribution with geologic formation. We find Boussingault (4) in Colombia in 1831, advancing the theory that an excess of calcium in the drinking water may cause endemic goiter. In 1850 Chatin (5), as a result of extensive iodine determinations in food, water and soil, concluded that a deficiency of environmental iodine was associated with the occurrence of goiter. These two theories—lack of iodine and the presence of various goitrogenic substances—have now abundant experimental and field observations to support them. An excess of iodine in the diet will usually prevent the formation of a goiter in a normal individual, but when the available iodine is at a critical level, then the presence of a goitrogen may tip the scales in favor of thyroid enlargement.