: I am also not certain about the use of the term "cretin" as it applies to hobbits which from Webster's II means "A deformed idiot". Certainly, Tolkien didn't mention any deformity in Sam, Frodo, Merry, Pippin or Bilbo (and those have the largest body of text describing them. Of course Frodo had a cleft chin, but I believe some people find that to be endearing and even attractive rather then a deformity. Obviously, Kirk Douglas was never referred to in this fashion.

I believe that cretinism is caused by an iodine deficiency during pregnancy. Do we have any evidence that the soil in the area of the Shire was deficient in this element? If so that may possibly explain the small stature of Hobbits although it does not explain the lack of other typical symptoms of cretinism such as extremely sloped forehead, receding chin and poor intellectual development.

I think we would have to rule out cretinism unless you assume that the area in the vales of Anduin where Gollum's people lived was also deficient in iodine. The clincher though has to be Bree where 'normal' people and Hobbits lived in close proximity - iodine deficiency would have affected the whole population. Unless the Hobbits only ate food imported from the shire which I deem to be unlikely in the extreme.