Silent corticotroph adenoma: case report and literature review.

OBJECTIVE

To review the initial clinical manifestations and diagnosis of silent corticotroph adenoma.

METHODS

We report a case and summarize the relevant literature.

RESULTS

A 52-year-old patient with hypopituitarism underwent resection of a silent corticotroph adenoma. A circulating species was detected postoperatively, reactive in a highly sensitive adrenocorticotropic hormone (ACTH) 1-39 immunoradiometric assay (IRMA) and beta-endorphin or beta-lipotropin radioimmunoassay. The basal morning cortisol concentration consistently was <10 microg/dL. Dynamic testing was performed to screen for Addison's disease, congenital adrenal hyperplasia, and Cushing's syndrome. During dexamethasone suppression, the molar concentration of circulating ACTH precursors by a two-site IRMA was 55-fold greater than the concentration of ACTH 1-39 by IRMA. We concluded that the tumor displayed impaired processing of pro-opiomelanocortin (POMC) and secreted a bioinactive POMC-derived peptide that was reactive in the ACTH 1-39 IRMA.

CONCLUSION

Patients with silent corticotroph adenoma do not have clinically evident Cushing's syndrome. In some cases, bioinactive ACTH precursors may be detected by a sensitive ACTH 1-39 IRMA.