Endocrine Abstracts

Introduction: Adrenocorticotropic hormone (ACTH) is a tropic hormone produced by the anterior pituitary that stimulates the adrenal glands to release cortisol. The ACTH measurement is often used to diagnose the pituitary and/or adrenal disorders, mainly Cushing’s disease, Cushing’s syndrome, Addison’s disease and hypopituitarism. Therefore, the assessment of plasma ACTH concentration is a crucial step in the differential diagnosis of hypothalamic–pituitary–adrenal axis dysfunction. The purpose of our study was to present a case of patient with unexpectedly high concentration of ACTH

Case details: A 63-year-old Caucasian man was referred to our clinic for hormonal diagnostics due to a tumor in the left adrenal gland found in an abdominal CT scan, which showed an 11×10 mm mass with attenuation of approximately 20 HU (Hounsfield unit) in the left adrenal gland. Contrast-enhanced magnetic resonance imaging showed an 11×13 mm tumor without features of a lipid-rich adrenal adenoma. Plasma ACTH levels were highly elevated with normal cortisol levels using chemiluminescent immunoassay (Immulite 2000Xpi). The 24-hour ACTH and cortisol secretion profiles in the serum of the patients were respectively 602.00 [pg/ml] and 19.10 [μg/dl] at 0800 h, and 539.00 [pg/ml] and 3.12 [μg/dl] at 1000 h. Cushing’s disease (due to an ACTH-secreting pituitary tumor) was ruled out by a low-dose dexamethasone suppression test, and Addison’s disease (adrenal insufficiency) was ruled out by a normal Synacthenem short test. No pathological changes were found on MR imaging of the pituitary. In addition, polyethylene glycol 25% (PEG) precipitation and serial dilutions were applied to the serum. After PEG precipitation, ACTH decreased from 331 to 18.92 [pg/ml] (recovery: 5.72%). Endocrine diagnostics showed no hormonal activity of the adenoma in the left adrenal gland.

Conclusion: Macro-ACTH should be suspected when elevated ACTH levels are not consistent with clinical picture. Consideration of alternative testing methods, including PEG precipitation testing and clinical assessment, are of paramount importance in making the correct diagnosis. Strict cooperation between the physician and the laboratory is important in the approach to such cases.