11C-5-hydroxytryptophan PET scan in diagnosis of ectopic Cushings syndrome from typical lung carcinoid: a case report
Djuro Macut1, Svetozar Damjanovic1, Jelica Bjekic2, Bojana Popovic1, Ivana Bozic1, Milan Petakov1, Sanja Ognjanovic1, Tanja Isailovic1, Miloje Joksomovic3, Radoslav Jakovic4, Jelena Mirkovic1 & Jelena Stojsic4
A 34-year-old woman was initially presented with clinical signs of Cushings syndrome (CS). On endocrinological examination, a diagnosis of ACTH dependent CS was established (serum cortisol: 08.00 h: 1245 nmol/l; 24.00 h: 275; plasma ACTH concentration 104 ng/l; inadequate cortisol suppresion on LDDST (787) and suppresion to 318 following HDDST). A magnetic resonance imaging (MRI) confirmed a microadenoma in the left part of the pituitary. Ultrasound examination confirmed hyperplastic adrenals. Hypercortisolism persisted after the transsphenoidal operation of the pituitary adenoma; immunohistochemical staining was positive only on FSH and LH. Subsequently, she developed ankle edema, hypokalemia and hormonal profile suggestive on ectopic CS (plasma ACTH 171.9 and failure to suppress serum cortisol following HDDST) confirmed by CRF and DDAVP test. Neuroendocrine origin of the ectopic ACTH production was further suspected with elevated chromogranin A (489.2 ng/ml). Normal levels of 5-HIAA and PTH were obtained. A genetical analyses excluded mutation in menin. A subsequently repeated CT/MRI scans of neck, thorax, abdomen and pelvis were negative. Scintigraphy with 111In-pentreotide did not show any accumulation of the tracer in the body. Whole-body chateterization and sampling did not reveal an ectopic ACTH source. Positron emission tomography (PET) using 11C-5-hydroxytryptophan (5-HTP) (Uppsala, Sweden) showed increased tracer uptake in the retrocardial region of the left lung. In meantime, octreotide in a dose of 900 μg/day s.c. was applied producing complete normalizatioon of arterial blood pressure, restoration of menstrual cyclicity, and complete normalization of cortisol and ACTH. She was successfully operated 14 months after the onset of first signs of CS with pathological confirmation of 11 mm typical lung carcinoid. We presented an unusual case of ectopic CS produced from the typical lung carcinoid that was detected only by means of 5-HTP PET, and associated with coincidentally diagnosed gonadotroph pituitary adenoma.