Endocrine Abstracts

In ACTH-dependent Cushing’s syndrome, the high dose dexamethasone suppression test (HDDST) has been traditionally used to identify differentiate between pituitary-dependent Cushing’s disease and ectopic ACTH production. However, more recently, concerns regarding the diagnostic accuracy of the HDDST have led to many centres abandoning this test in preference to bilateral inferior petrosal sinus sampling (IPSS). We aimed to establish current consensus in the UK for the diagnosis of Cushing’s disease, with particular reference to the HDDST and IPSS. A questionnaire was constructed and circulated to the audience attending the ‘Medical Management of Cushing’s disease’ session at the European Congress of Endocrinology on 4th April 2006.

The questionnaire was completed by 128 endocrinologists. The HDDST was the most widely used test (90%) in distinguishing Cushing’s disease from Cushing’s syndrome, with only 39% of clinicians employing IPSS. The majority of responders (83%) routinely use HDDST in the diagnosis of Cushing’s disease compared to 17% who do not. Similarly, 84% of endocrinologists felt that the HDDST remained a useful diagnostic test in the diagnosis of Cushing’s disease. Interestingly, the availability of IPSS was limited to 52% of clinicians completing the questionnaire, which may have influenced the responses regarding HDDST. The most commonly used tests (in order of preference) to distinguish Cushing’s disease from Cushing’s syndrome due to an ectopic ACTH source were HDDST (77%), IPSS (65%), pituitary imaging (61%) and the CRH stimulation test (63%). Clinicians did not find the plasma ACTH useful (4%).

These findings demonstrate that the HDDST remains widely used in the UK in the diagnosis of Cushing’s disease. However, the widespread use of the HDDST may have been influenced by the finding that only approximately half of responders had IPSS available at their centre.