Endocrine Abstracts

Background: If the laboratory results are not compatible with the patient’s clinical symptoms, the presence of possible test interference should be considered. Despite the excellent quality of immunoassays, it is currently estimated that they may be susceptible to several types of interference that may lead to patient misdiagnosis.

Case report: In our case report we present a 71-year-old woman with confirmation of macro-adrenocorticotropic hormone (macro-ACTH). A magnetic resonance imaging (MR) scan revealed macroadenoma of the pituitary gland (size 16×12×14 mm). Laboratory tests revealed repeatedly high plasmatic levels of adrenocorticotropic hormone (without clinical manifestation of hypercortisolism or hypocortisolism), normal plasma cortisol levels with circulating variation and normal 24 – urine free cortisol. Plasmatic levels of another pituitary hormones were normal. A 2 mg and 8 mg dexamethasone blockade were performed with adequate cortisol suppression. Short synacthen test excluded adrenal insufficiency. Due to the suspicion of the presence of interference, we performed precipitation with polyethylene glycol (PEG-precipitation), which confirmed the high probability of the presence of macro-ACTH.

Conclusion: Although the presence of macrohormones is rare, some cases appear in clinical practice, which must be resolved through differential diagnosis. Systematic search for these interferences in clinical practice is not recommended, but an active approach to interference detection can prevent patient misdiagnosis. In our patient, despite the confirmed diagnosis of macro-ACTH, the trans-sphenoidal resection was performed. Histopathologic and immunohistochemical findings revealed non-functioning pituitary adenoma.