People living in the low Himalayan hilly regions often suffer from goitre. What could be the possible reason for it ?

Goitre is caused due to IODINE deficiency. We get it mostly from salts.. In the coastal areas, we have more amount of salt.. so the food produced there is rich in salt content.. where as the hilly areas much far away from sea coast, enough salt content is not so . This causes the deficiency of iodine which in turn causes goitre.