Endocrine Abstracts

Introduction: Ipilimumab is a monoclonal antibody directed against CTLA-4 used primarily in treatment of malignant melanoma. Immunological side effects are common, amongst others it may lead to hypophysitis. We studied clinical characteristics of IpiH and compared it to cases of primary hypophysitis (PH).

Methods: We conducted a retrospective single centre study in 75 hypophysitis patients (60 primary, 15 Ipilimumab-induced in patients with melanoma). Group differences were calculated using Mann-Whitney U test or chi-square test.

Results: Nominally, the number of affected pituitary axes did not significantly differ between groups (mean 2.5±1.3 in IpiH vs. 1.9±1.3; P=0.13). Deficiency of anterior pituitary axes did not significantly differ between both groups. However, IpiH patients had less often diabetes insipidus (13% vs. 38%, P=0.044) and none had hyperprolactinemia as sign of pituitary stalk damage (0% vs. 25%, P=0.045). Male patients had significantly more gonadotropin deficiency than their female counterparts (IpiH: 88.9% vs. 16.7%, P=0.005; PH: 75.0% vs. 30.2%, P=0.002). Other axes showed no differences in sex distribution. Patients with IpiH didn’t develop any further deficiency whereas 23.2% of PH-patients had further axes affected during follow-up. IpiH was diagnosed 2 months (median) after initiation of Ipilimumab treatment.

Discussion: Patients with IpiH have less diabetes insipidus and hyperprolactinemia than patients with PH. Possibly, IpiH seldomly involves the pituitary stalk. The course of IpiH seems more favorable as no further pituitary deficiency after diagnosis was observed in our cohort. Our findings show subtle differences between IpiH and PH, especially concerning neurohypophysis.