An Unusual Etiology of Hypothyroidism and New-Onset Insulin-Dependent Diabetes: A Rare Side Effect of Nivolumab

Nivolumab, a monoclonal antibody targeting programmed cell death 1 receptor, is prescribed for many advanced cancers like malignant melanoma, non-small cell lung cancer, renal cell cancer, etc. With the increase in the use of nivolumab like immunotherapy, the incidences of immune-related side effects are also on the rise. Immune-related endocrinopathies like hypothyroidism and new-onset type 2 diabetes mellitus associated with nivolumab use, although rare, are already documented in the literature. Here we present a case of hypothyroidism and new-onset type 2 diabetes mellitus in a renal cell cancer patient receiving nivolumab for the past six months. The patient was managed successfully with discontinuation of nivolumab, intravenous insulin, and thyroid hormone replacement therapy. These types of endocrinopathies can be fatal; hence, prompt diagnosis and management are required. Thus, not only physicians’ awareness of such endocrinopathies among nivolumab-treated patients but also patients’ awareness regarding warning signs and symptoms are essential.