CTLA4 and diabetes mellitus: Expert endocrinologists met three times between October 2017 and April 2018, and formulated an expert opinion based on an exhaustive literature review (using PubMed) with the search terms ‘ICPI, CTLA-4, PD-1, PD-L1, diabetes, hypophysitis, thyroiditis, adrenal insufficiency’, over the period 1990–2018.