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

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "cretinism":
   acromegaly, amentia, arrested development, backwardness,
   blithering idiocy, choriocarcinoma, diabetes, diabetes insipidus,
   diabetes mellitus, dwarfism, giantism, half-wittedness,
   hyperglycemia, hyperparathyroidism, hypo-ovarianism,
   hypothyroidism, idiocy, idiotism, imbecility, infantilism,
   insanity, mental defectiveness, mental deficiency, mental handicap,
   mental retardation, mongolianism, mongolism, mongoloid idiocy,
   moronism, moronity, panhypopituitarism, pheochromocytoma,
   profound idiocy, retardation, retardment, sexual precocity,
   simple-wittedness, simplemindedness, simpleness, simplicity,
   subnormality, thyrotoxicosis, toxic goiter