Acromegaly — Clinical Features

A 52-year-old man presents to the endocrinology clinic with progressive coarsening of facial features, macroglossia, and markedly enlarged hands with a "spade-like" appearance (shown as **A** in the diagram). His wife reports he has required progressively larger shoe and ring sizes over the past 8 years. Serum IGF-1 is elevated at 680 ng/mL (normal: 90–360 ng/mL for his age). An oral glucose tolerance test shows failure of growth hormone to suppress below 1 ng/mL after 75 g glucose load. Pituitary MRI reveals a 2.2 cm sellar mass with suprasellar extension. Which of the following is the MOST LIKELY pathophysiology underlying the clinical phenotype marked **A**?

A 52-year-old man presents with progressive facial coarsening, jaw enlargement, and deepening of voice over the past 8 years. His wife reports he now snores loudly and frequently stops breathing during sleep. On examination, the structure marked **A** in the diagram is evident, along with macroglossia and thickened skin. His serum IGF-1 is elevated at 3.2 times the upper limit of normal. An oral glucose tolerance test shows a GH level of 3.5 ng/mL after 75g glucose load. MRI pituitary reveals a 1.8 cm sellar mass. Which of the following is the most likely diagnosis?