ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2008) 16 P150

Subclinical Cushing's syndrome (CS): role of 131I-iodomethylnorcholesterol scintigraphy in predicting the evolution of the disease

Rosa Maria Paragliola1, Pietro Locantore1, Maria Pia Ricciato1, Vittoria Rufini2, Germano Perotti2, Carlo Antonio Rota1, Alfredo Pontecorvi1 & Salvatore Maria Corsello1

1Department of Endocrinology, Catholic University School of Medicine, Rome, Italy; 2Department of Nuclear Medicine, Catholic University School of Medicine, Rome, Italy.

Subclinical CS, mild hypercortisolism without overt clinical manifestations, is the most frequent (5–8%) hormonal abnormality detected in patients with secreting adrenal incidentalomas.

Unclear clinical features and mild hypercortisolism make the diagnosis problematic, although laboratory criteria have recently been reviewed. In these cases, scintiscan is a central tool to define the adrenal functional activity.

A 60-year-old man was referred to us because of hypercolesterolemia and hypertension treated by calcium-antagonists and alpha-lytics.

CT performed because of suspected kidney stones showed a 4 cm right adrenal mass with radiological features indicative for adenoma.

The adrenal ‘incidentaloma’ was evaluated for possible hypersecretion: screening tests for primary hyperaldosteronism and pheochromocytoma were negative.

Circadian rhythm in serum cortisol concentration and urinary free cortisol (UFC) were normal. Plasma ACTH concentration was low (7 pg/ml). Overnight dexamethasone 1 mg suppression test (DST) was uncertain: serum cortisol at 8 AM was 21 ng/ml.

131I-iodomethylnorcholesterol scintigraphy showed unilateral uptake on the side of the adrenal mass (concordant uptake).

Because of the borderline biochemical findings and subclinical presentation, careful observation associated with treatment of metabolic syndrome was preferred. A new evaluation was planned after 6 months. At that time a marked increase of urinary free cortisol, elevated midnight cortisol and nonsuppressible cortisol (60 ng/ml) after 1 mg DST were observed. ACTH was less than 5 pg/ml. Abdominal CT was unchanged. Furthermore, in spite of medical therapy, a worsening in metabolic and blood pressure control was detected. Therefore the patient underwent surgery. Postsurgical hypoadrenalism is currently treated by HC.

This case confirms the usefulness of radiocholesterol scintigraphy in detecting adrenal hyperfunction in patients with subclinical CS. An incidental mass showing unilateral concordant radionuclide uptake in spite of the absence of clear clinical and laboratory findings is predictive of a possible evolution in overt CS and makes necessary a close follow up.