Can hypothyroidism be prevented?

Simple answer is no: Unless the cause of your hypothyroidism is induced by medication (such as lithium or amiodarone). In underdeveloped countries where iodine deficiency is present, prevention can be made by supplementing diet with iodine. That is not the case here in the US as our food chain (bread, table salt, etc) is enriched with iodine. No prevention currently exists for autoimmune thyroid diseases.

Some: Hypothyroidism cause by nutrient deficiencies might be prevented by making sure you are not deficient in iodine, selenium, iron, b12, and others micronutrients.