Endocrine Abstracts

Purpose

Inferior petrosal sinus sampling (IPSS) is the gold standard test for the differentiation of pituitary Cushing disease from the ectopic ACTH syndrome (EAS). The measurement of prolactin during IPSS can be helpful to improve the accuracy of the procedure. We aimed to evaluate the effect of measuring prolactin levels as a predictor for the accuracy of IPSS procedure and evaluate its’ impact on the lateralization of adenoma.

Material and methods

In this retrospective cohort study, we reviewed 51 patients who had undergone IPSS for the investigation of ACTH-dependent hypercortisolism at Marmara University E&R Hospital between 2012 and 2019. Plasma ACTH (adrenocorticotropic hormone) and prolactin levels were measured both centrally and peripherally during IPSS procedure in all patients. The prolactin adjusted ACTH inferior petrosal sinus/peripheral (IPS/P) ratio was calculated to assess the accuracy of the sampling procedure.

Results

Forty-nine patients had proven CD, one was EAS. Forty-seven patients had above two ACTH IPS/P ratio at baseline, and all the proven CD patients’ post-corticotropin releasing hormone (CRH) ACTH IPS/P ratio was above three. Prolactin IPS/P ratio was above 1.8 in all patients. While prolactin adjusted ACTH IPS/P ratios were >1.3 in all patients with proven Cushing’s disease, it was 0.7 in the patient with EAS. Both baseline ACTH and prolactin levels were positively correlated with post-CRH ACTH and prolactin levels (r:0.735, p<0.001; r:0.910, p<0.001, respectively). While post- CRH, ACTH levels were significantly increased from baseline to 3rd, 5th, 10th minutes in the P and IPS samples (p<0.001), prolactin levels were not showed a statistically significant increase after stimulation with CRH both in the P and IPS samples (p:0.116, p:0.712). Positive lateralization was observed in 55.1% of patients with ACTH gradient, but when prolactin adjusted ACTH IPS/IPS ratio used in addition to the ACTH gradient, the ratio was increased to 67.3%.

Conclusion

Prolactin IPS/P ratios are useful to define successful catheterization, and prolactin adjusted ACTH IPS/P ratio can be helpful to improve the accuracy of results during IPSS procedure.