You are answering a USMLE-style medical question. Question: A 30-year-old man presents to his primary care physician with complaints of excessive fatigue and weakness for the last several weeks. He also complains of abdominal pain and constipation for the same duration. On further questioning, he reports that he has lost 8 pounds in the last 2 weeks. Past medical history and family history are insignificant. His temperature is 37.3° C (99.2° F), respirations are 21/min, pulse is 63/min, and blood pressure is 99/70 mm Hg. On physical examination, he is a tired-appearing, thin male. He has a bronze discoloration to his skin, but he denies being outside in the sun or any history of laying in tanning beds. What is the next best step in the management of this patient? Options: A) Administer intravenous fludrocortisone B) Start him on androgen replacement treatment C) Start him on both hydrocortisone and fludrocortisone therapy D) Order an ACTH stimulation test Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.