Hypothyroidism is hereditary?

Hypothyroidism itself NO is inherited, except in certain cases in the context of certain extremely rare genetic syndromes. Now, what does that inherits is the "willingness" to having it in the form of genes both maternal and paternal side. From there, the atmosphere, toxic and many other factors come into play, and that will determine whether or not develop hypothyroidism.
Thus, a child of parents with hypothyroidism need not be too hypothyroid. A greeting.