The iodine cycle in the tropical environment — implications on iodine deficiency disorders

Iodine deficiency disorders are a major health problem in a large number of countries most of which lie within the tropical environment. Even though iodine may be abundant in the surface environment, its low bioavailability is the key issue that governs the incidence of IDD. In view of the intense rainfall in the tropical environment, rock weathering with accompanying clay formation and soil leaching is markedly high. Clayey matter and humic substances fix iodine strongly and these are potential geochemical goitrogens that could control the bioavailability of iodine significantly.