**Abstract**

The use of immunotherapies is gaining importance in the treatment of advanced malignancies. There are many checkpoints in the immune system which prevents T-cells from attacking one's own body cells. The cancer cells can camouflage from the T-cells and the immune system is unable to mount an effective anti-tumor response. The immunotherapies, mainly monoclonal antibodies anti-cytotoxic T-lymphocyte antigen 4 (CTLA-4), anti-programmed cell death protein-1 (PD-1) and anti-PD-1 ligand molecules (PD-L1 and L2) reactivate the immune system to act against cancerous cells but they can also cause T-cells to attack healthy cells causing various autoimmune diseases, which are known as immune related adverse events (irAEs). Current clinical data shows increased incidence of pituitary disorders with CTLA4 inhibitors and thyroid dysfunction in patients with PD-1/PD L-1 1 blockade. There have also been association of type 1 diabetes mellitus and primary adrenal insufficiency in patients with immune check point inhibitors. In this chapter we will discuss the incidence, characteristic findings, diagnosis and management of various endocrinological side effects due to targeted immunotherapies used in various malignancies.

**Keywords:** cancer immunotherapy, immune check point inhibitors, endocrine side effects, thyroid dysfunction, hypophysitis, primary adrenal insufficiency, Type 1 diabetes mellitus
