Endocrine Abstracts

Case History: 26 year old man with uncontrolled hypertension and weight gain over the last 10 – 15 years associated with abdominal stretch marks. His past medical history includes hypertension managed with four oral anti-hypertensive agents and a BMI of 36.74 kgm2 (with centripetal obesity). There is no family history of hypertension.

Investigations: However, there was historical biochemical evidence of hypokalaemia (between 2.6 – 3.2mmol/l) in the past year but his serum aldosterone levels was not elevated (renin 1.2 nmol/l/h, serum aldosterone <60 pmol/l). Further investigations include 24 hour urinary free cortisol (774 nmol/day), post ONDST serum cortisol (807 nmol/l) with serum ACTH 56.7 ng/dl. These were suggestive of possible Cushing’s disease. His enhanced MRI of the pituitary gland did not identify a discrete lesion and there was no enlargement of the pituitary gland noted. His CT scan of the abdomen revealed bilateral adrenal enlargements.

Results and Treatment: Given the high suspicion of ACTH-dependent Cushing’s syndrome, his case was discussed at our regional pituitary multi-disciplinary team meeting and further tests performed. These are: i) cortisol day curve that identified persistently elevated serum cortisol levels with non-suppressed ACTH); ii) elevated salivary cortisol levels taken on three occasions; iii) an elevated 9am serum cortisol level following repeat ONDST (380nmol/l); as well as iv) IPSS that revealed a central to peripheral ACTH gradient that excluded ectopic ACTH. He was then commenced on metyrapone 500mg BD and further cortisol day curves were performed to guide the up-titration of his metyrapone dose. His whole body DEXA scan revealed a BMD that is below the expected range for age at the lumbar spine and hips. NM Methionine PET/CT demonstrated heterogeneous tracer activity in pituitary gland with slightly higher activity towards the right and minor left lateral extension.

Conclusions and Points for discussion: Different imaging modalities having been utilised to evaluate ACTH dependent Cushing syndrome. We advocate the use of 11C Methionine PET CT in the evaluation of pituitary adenomas due to its high sensitivity and ability to detect lesions that may be difficult to identify on cross-sectional MRI sequences. Our case also highlights the importance of multidisciplinary approach in the timely diagnosis and management of patients with high suspicion of Cushing’s disease.

References: A role for 11C-methionine PET imaging in ACTH-dependent Cushing’s syndrome. Koulouri et al. Eur J Endocrinol 2015 Oct;173(4):M107-20. doi: 10.1530/EJE-15-0616. Epub 2015 Aug 5.