[Checkpoint inhibitors-induced hypophysitis]

Checkpoint inhibitors immunotherapy is more and more prescribed in oncology, causing new immune related endocrine adverse events. Hypophysitis occurs in approximately 10 % of patients treated with anti-CTLA4. It occurs two to three months after initiation of the immunotherapy. The initial presentation is characterized, in typical forms, by the association of headache, asthenia and hyponatremia. Hormonal exploration usually shows ACTH, gonadotropic and thyrotropic deficiencies. ACTH deficiency may be life-threatening and requires urgent supplementation, without awaiting for biological results. MRI is warranted in order to exclude differential diagnoses, such as pituitary metastases. Hypophysitis induced by anti-PD1/PDL1 seems to be a different nosologic entity characterized by a later onset and a less symptomatic presentation. Biologically ACTH deficiency seems to be constant and permanent, and often isolated. Treatment requires high-dose steroids only in case of severe tumor syndrome (resistant headache, visual disturbance) or acute decompensation of ACTH deficiency. Patients always need lifelong hormonal supplementation of pituitary deficits and must be followed and educated specifically. Immunotherapy can be delayed during the acute phase, but can be secondarily continued if there is an oncological benefit. As it is a pauci-symptomatic but potentially life-threatening complication, biological screening must be systematic in patients treated with checkpoint inhibitors.