ACTH-producing adenoma of the pituitary gland manifesting as severe insulin resistance

Pituitary adenomas are commonly benign neoplasms which may manifest with a wide variety of symptomatology. Typically, ACTH- producing tumors of the pituitary gland present with central fat deposition, abdominal striae, moon facies, buffalo hump, osteoporosis, hypertension, hirsutism, gonadal dysfunction, immunosuppression, and less commonly with hyperglycemia due to insulin resistance. We report the case of a 58-year-old male patient with an ACTH producing pituitary microadenoma and type 2 Diabetes Mellitus (DM) whose primary presenting symptom was increasing insulin resistance despite appropriate adjustments to his insulin therapy. Bilateral inferior petrosal sinus sampling showed results highly suspicious for a left sided pituitary microadenoma. Endoscopic endonasal transsphenoidal resection of the pituitary tumor was performed to resect the microadenoma of the left gland. This case adds to the diverse presentations of pituitary adenomas, in that these lesions must be included in the differential diagnosis of a type 2 DM patient with hyperglycemia and insulin resistance.