<prompt> Answer this question truthfullyWhat is subperiosteal thinning and which hormone can cause it to occur in the clavicles, phalanges, and skull?  <response>: <reason> Subperiosteal thinning is a condition where the outer layer of bone periosteum becomes thinner, and it can occur in the clavicles, phalanges, and skull due to elevated parathyroid hormone PTH. 