A 9-yeаr-оld bоy is brоught to the clinic due to his short stаture. The mother is concerned thаt her son is not as tall as his classmates, causing him stress. On physical exam, there is macrocephaly with frontal bossing, shortening of the arms and legs, and lumbar lordosis. Which of the following physiologic processes is most likely disrupted in this patient’s condition?