This is a single center trial to determine the effect of CRH stimulation on (18)F-FDG uptake in high-resolution PET-imaging of ACTH-adenomas in CD patients. CD patients will undergo (18)F-FDG high-resolution PET-imaging without CRH stimulation and (18)F-FDG high-resolution PET-imaging with intravenous CRH stimulation. The order of the PET scans will be randomized and the second PET scan will occur greater than 24 hours but less than 14 days after initial PET-imaging. For (18)F-FDG PET-imaging with CRH stimulation, intravenous (18)F-FDG will be given just before CRH administration. The PET images will be read by radiologists who are blinded to the administration of CRH. Within 12 weeks after completion of the last (18)F-FDG high-resolution PET-imaging scan, patients will undergo surgical resection of the pituitary adenoma. Surgical and histological confirmation of adenoma location will be used to assess the diagnostic and localization accuracy of PET-imaging and to compare to preoperative MR-imaging results in CD patients. Inferior petrosal sinus sampling (IPSS) results will be compared with imaging results and with surgical and histological findings.