Source
The Program in Reproductive and Adult Endocrinology, The Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892-1109, USA.
Abstract
CONTEXT:
Inferior petrosal sinus sampling (IPSS) best discriminates between the two causes of ACTH-dependent Cushing's syndrome, Cushing's disease (CD) and ectopic ACTH secretion (EAS). However, when sampling is not available, adjunctive diagnostic tests might be helpful. Neuroendocrine tumors may secrete chromogranin A (CgA), calcitonin (CT), procalcitonin (ProCT), a fragment of the amino terminus of procalcitonin (NProCT), and/or ACTH.
OBJECTIVE:
The aim of the study was to evaluate the ability of serum CgA, CT, ProCT, or NProCT values to distinguish CD from EAS.
DESIGN AND SETTING:
We conducted a prospective pilot study at a clinical research center.
SUBJECTS AND METHODS:
Serum ProCT, NProCT, and CgA were measured in six patients with occult EAS diagnosed by IPSS, 25 CD patients, and 11 patients with histologically proven EAS.
RESULTS:
Nine EAS patients (53%) had at least one value above the reference range, including CgA alone (n = 4), ProCT alone (n = 3), CgA and ProCT (n = 1), and NProCT and ProCT (n = 1). Of nine (36%) CD patients with one or two abnormal values, seven had increased ProCT only, one had increased NProCT only, and one had increased CgA and ProCT. CgA had a positive predictive value of 83% and a negative predictive value of 70% for the diagnosis of EAS; other markers showed less discrimination. On pituitary magnetic resonance imaging, no EAS patient had an abnormality, whereas 21 of 25 patients with CD had a mass.
CONCLUSION:
These preliminary results suggest that an abnormal CgA and normal pituitary magnetic resonance imaging favor the diagnosis of EAS, but normal tumor markers do not exclude the diagnosis.