When it comes to preventing hypothyroidism, there really isn't anything most people can do to stop the onset of the disorder.
There are some countries, particularly in Southeast Asia and Africa, where iodine deficiency is common. Many countries have combated iodine deficiency with iodized salt. But in those countries where salt isn't often consumed, or the element isn't added to salt, taking iodine supplements may help prevent hypothyroidism.
But if you live in a developed country, such as the US, most diets contain adequate amounts of iodine. That said, there's no known way to prevent hypothyroidism if you are taking in enough iodine.
Fortunately, you can prevent hypothyroidism from becoming a serious health issue. By understanding the risk factors, recognizing your symptoms, and getting diagnosed early on, you will prevent serious complications that can occur if hypothyroidism is left untreated.