Minerals (as the term is used in nutrition, not in mining) are chemical elements, not "compounds". They are part of the constituents that can be synthesised into compounds. Usually our bodies obtain them in some form of organic or inorganic salts, which are compounds, so we obtain them as parts of compounds. To synthesise compounds that contain iodine, you need iodine in some form. As we are not talking about nuclear reactions through which elements are synthesised through other elements, there is no way humans, animals or plants synthesise any minerals like iodine, we all obtain them from some source. The original sentence is weird, because it talks as if iodine can be synthesised somehow chemically but just our bodies are unable to.