Step 1: Growth Hormone (GH) is secreted by the anterior pituitary gland.
Step 2: If GH is secreted in excess during childhood, before epiphyseal plates close, it leads to gigantism.
Step 3: If GH is secreted in excess during adulthood, after epiphyseal plates have closed, it leads to acromegaly.
Step 4: Acromegaly is characterized by enlargement of hands, feet, jaw, and facial bones.