Endocrine Abstracts

Introduction: Inferior petrosal sinus sampling (IPSS) is considered to be the gold standard for confirming the source of ACTH secretion in patients with Cushing’s syndrome (CS). Prolactin measurement during IPSS can improve diagnostic accuracy and reduces false negative responses.

Patients and methods: 56 patients with ACTH-dependent CS were included (45 F/11 M, mean age 43.6±10.8 years and 90.1% Cushing’s disease) diagnosed since 2000. IPSS was performed in 27 cases (15 with PRL measurement, two excluded due to incomplete data). Depending on IPSS results were classified as typical IPSS response if basal ACTH ratio Central/peripheral (C/P) was >2 and/or after CRH >3, considering others as atypical. Response to surgical treatment and utility of PRL determination were analyzed.

Results: Cortisol response to high DXM suppression test was >50% in 62.9%, and >90% in 37% in Cushing’s disease. Preoperative pituitary MRI did not identify adenoma in 12.5%. MRI adenoma lateralization was concordant with surgical adenoma lateralization in 92.7%. IPPS was typical in 46.3% (6/13) and there were significant differences typical vs atypical (basal ACTH C/P ratio, ACTH C/P ratio after CRH, peak time, urinary free cortisol (UFC) and PRL correction). Basal PRL ratio C/P was <1.8 in all atypical IPPS and 50% of typical IPPS. Venograms were reviewed and ACTH C/P peak corrected with PRL was >0.8 in Cushing’s disease, being most of them >1.2 (5/7). Only two patients have an intermediate value (a cyclic Cushing’s disease 1.09 and a microadenoma 1.05). Four patients with atypical IPPS corrected with PRL were referred to surgery and they meet remission criteria up today. After transsphenoidal surgery 90.9% of patients met remission criteria (100% of microadenomas and in those without previous MRI image).

Conclusion: PRL measurement in atypical IPSS allows reclassification, whereas in typical cases can be useful to validate the peak ACTH C/P. PRL elevation after CRH and its use in the correction of the ACTH C/P ratio does not interfere with the interpretation of ACTH C/P peak. It is essential to evaluate UFC to complete the assessment