Endocrine Abstracts

Introduction: IPSS (Inferior petrosal sinus sampling) is a reliable test for differentiating Cushing’s disease from ectopic ACTH secretion. In the past 30 years, Hadassah Hebrew University Hospital has been the sole national referral center for IPSS in Israel, carrying out the test for all patients country-wide.

Methods: In this retrospective study we reviewed the records of all patients who underwent IPSS in our institution, for whom electronic data were available. Medical records were reviewed, and additional information was collected from the referring endocrinologists.

Results: Between 2003 and 2019 IPSS was performed in 63 patients. Male/female ratio was 19/44 and the average ± s.d. age was 45.1 ± 14.9. Indications for referral included: absence of a visible pituitary adenoma on MRI (43patients, 68.3%); inconclusive biochemical testing (16 patients, 25.4%); and persistent hypercortisolemia following prior pituitary surgery (12 patients, 19.0%). Over one indication per patient may have been listed. IPSS results compatible with pituitary ACTH secretion were found in 52/63 patients (82.5%), of whom 48/52 (92.3%) underwent subsequent pituitary surgery. Biochemical cure was reported for 31/52 patients (59.6%) and 6/52 (11.5%) had residual or recurrent disease, although pathological results indicated pituitary adenoma. Thus, in 37/52 (71.2%) patients with IPSS results compatible with pituitary ACTH secretion, Cushing’s disease was confirmed. The final outcome was unknown in 15/52 (28.8%) patients, of whom 4 did not undergo surgery and in 11 hypercortisolemia did not resolve following surgery and confirmatory pathology results were unavailable. IPSS test results were consistent with ectopic ACTH secretion in 11/63 patients (17.5%). A documented ACTH secreting ectopic tumor was discovered in 4 patients (1 medullary thyroid carcinoma and 3 carcinoid), 3 were found to harbor an adrenal adenoma and in 2 the source of ACTH hypersecretion was not found. Pituitary surgery was performed in two patients in spite of IPSS results indicating an ectopic source of ACTH, and their hypercortisolemia had subsequently resolved. Overall, IPSS correctly established the diagnosis in 44 (69.8%) patients – accurately revealing a pituitary source in 37 patients and a non-pituitary source in 7 patients. A false negative result was noted in 2 patients (3.2%). The high rate of inconclusive outcomes (17/63, 27.0%) precludes reliable estimation of sensitivity and specificity of the test. No major complications of the IPSS procedure were documented.

Conclusions: In this select population of diagnostically challenging patients with Cushing syndrome, IPSS was safe and feasible, and led to definitive diagnosis in 69.8% of the patients.