The Collaborative International Dictionary of English v.0.48:

Cretinism \Cre"tin*ism\ (kr[=e]"t[i^]n*[i^]z'm), n. [F.
   cr['e]tinisme.]
   A condition of endemic or inherited idiocy, accompanied by
   physical degeneracy and deformity (usually with goiter),
   frequent in certain mountain valleys, esp. of the Alps.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cretinism
    n 1: severe hypothyroidism resulting in physical and mental
         stunting