You are answering a USMLE-style medical question. Question: A 34-year-old man comes to the physician because of frequent headaches and blurry vision during the past 4 months. He has also had difficulties achieving an erection over the past few weeks. Physical examination shows a temporal visual field deficit bilaterally. An MRI of the brain shows an intrasellar mass. The mass is most likely derived from which of the following types of cells? Options: A) Thyrotrophs B) Lactotrophs C) Somatotrophs D) Gonadotrophs Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.