Endocrine Abstracts

Large corticotroph adenomas are uncommon pituitary mass lesions, representing around 10% of cases of Cushing's disease, and are often found to be locally invasive. 'Silent' corticotrophinomas stain for ACTH, but do not secrete sufficient ACTH to cause Cushing's disease. We describe a patient with an unusual mass presentation of a pituitary adenoma in whom there was also a marked discrepancy between the clinical and laboratory findings in the assessment of suspected Cushing's disease. A 54 year old woman presented with symptoms of nasal obstruction; CT showed a mass in the nasopharynx, and biopsy demonstrated an ACTH positive pituitary adenoma. She had a classic Cushingoid appearance, with facial plethora, thin skin, dorsal fat pad, hypertension and diabetes. MRI showed a large pituitary mass compressing the hypothalamus and invading the sphenoid sinus. Despite her strikingly Cushingoid appearance, there was no biochemical evidence of cortisol excess (UFC 125 nmol/24hr, LDDex: serum cortisol 66 nmol/l at 48h). She underwent trans-sphenoidal surgery twice, resulting in marked loss in weight. Three months after surgery she had low 9 am cortisol levels (126-184 nmol/l); in contrast, however, UFC rose from 23 to 940 nmol/24h at this time. The cortisol response to insulin-induced hypoglycaemia was suboptimal: peak cortisol 346 nmol/l. This case demonstrates an unusual presentation of a large invasive 'silent' corticotrophinoma, with nasal obstruction and features of cortisol excess. The clinical appearance of Cushing's disease was not borne out by initial tests; we believe that the tumour had caused cortisol excess in the past, leading to the Cushingoid features. Post-operative cortisol levels have been variable and inconsistent, supporting the clinical view that this large corticotrophinoma secretes ACTH intermittently. In patients with clinical features of Cushing's syndrome and normal cortisol studies, a diagnosis of intermittently-active large corticotrophinoma should be considered.