Cyclic Cushing syndrome due to an ectopic pituitary adenoma

Background A 39-year-old man was referred to an endocrinology clinic for evaluation of his Cushing syndrome. He had gained 20 kg over 5 years and complained of intermittent headaches and easy bruisability. His medical history included a left foot fracture associated with minimal trauma 2 years earlier, hypertension, and stable Crohn disease with no use of exogenous glucocorticoids for at least 10 years. Investigations Measurements of plasma adrenocorticotropic hormone, 24 h urine free cortisol excretion, late-night salivary cortisol, serum cortisol levels before and after corticotropin-releasing hormone administration during a dexamethasone suppression/corticotropin-releasing hormone-stimulation test, pituitary MRI, and inferior petrosal sinus sampling. Diagnosis Cyclic Cushing syndrome secondary to an ectopic pituitary adenoma. Management The cyclic nature of Cushing syndrome was suggested by the absence of hypercortisolemia during inferior petrosal sinus sampling, and was confirmed by multiple 24 h urine free cortisol measurements. The patient underwent transsphenoidal surgery, during which a 5 mm firm, round, midline sphenoid sinus lesion was identified and resected. In preoperative imaging studies, this lesion had been interpreted as being a mucosal polyp. At microscopic examination, the lesion was found to be a pituitary adenoma, which stained diffusely with antiadrenocorticotropic-hormone antibodies. Explorations of the sella and pituitary did not reveal any abnormalities. Postoperatively, the patient became hypocortisolemic and his cushingoid features resolved. His adrenal function normalized 3 months after surgery. At 18 months, the patient continued to be symptom-free with normal levels of urinary-free cortisol and midnight salivary cortisol.