gms | German Medical Science

Objective: Diagnosis and treatment of ACTH-dependent hypercortisolism are challenging. We are confronted with two major problems: The distinction between ACTH overproduction due to pituitary lesion from ectopic ACTH production is not always obvious in conventional biochemical tests. Localization of pituitary lesions is the second problem as microadenomas are often missed in MRIs. To clarify the diagnosis, we performed bilateral ACTH sampling in BIPSS. We have analyzed our experience with BIPSS and evaluated ist predictive value for tumor lateralization.

Method: We reviewed the data of patient, who underwent BIPSS between 2011–2013. Prior to BIPSS, standard biochemical investigations such as circadian rhythm of cortisol level, dexamethasone suppression tests and CRH stimulation tests were performed. All the patients received appropriate MRI. During catheterization, the timing of the ACTH sampling before and after CRH stimulation was as follows: –5, 0, 5, 10 and 15 min. Prolactin was measured as an index of pituitary venous drainage. Diagnostic criteria included the central vs peripheral ACTH ratio (IPS:P) and central right vs central left ratio.

Results: 13 out of 20 patients with hypercortisolism showed no clear sella MRI findings. These patients underwent BIPSS. Successful bilateral IPS catheterization rate was 92%. 11 patients obtained an IPS:P ratio 3–83 suggesting Cushing's disease. 1 patient showed ectopic ACTH secretion, one patient presented with Nelson's syndrome. 10 patients showed central right to left ACTH gradient of 3–78 after CRH provocation. 1 patient showed no side gradient. 11 patients underwent surgery. In only 2 patients was the tumor lateralization in IPS ’incorrect’ – a microadenoma was found on the contralateral side. In 1 of these 2 cases cavernosus sinus thrombosis caused restricted venous drainage and thus a low ACTH level on the ipsilateral side. In this case, BIPSS cannot be used to guide surgical resection. The accuracy for lateralization was 82% in our population. Altogether 8 of 11 patients showed remission after surgery. No major complication occurred during BIPSS.

Conclusions: IPS Sampling is an invasive investigation in the diagnosis of Cushing's syndrome. In our population, it turned out to be a method with a high success rate. It's a powerful tool to distinguish central ACTH overproduction from etopic ACTH secretion. Despite early controversy, we believe that BIPSS can be applied for the preoperative localization of pituitary microadenomas when MRI studies are not clear.