INS and obesity due to melanocortin 4 receptor deficiency: Furthermore, despite the wide use of oral glucose tolerance test (OGTT) in the clinical practice and research settings to evaluate pancreatic β-cell secretory capacity [17], there is a lack of standardization in which commonly used BCF indices, such as the basal insulin secretion index homeostasis model assessment of β-cell function (HOMA-β), the early phase insulin secretion index (e.g. ΔI30/ΔG30, CIR30) and the late phase insulin secretion index (e.g. AUCI60–120/AUCG60–120, CIR120), better reflect BCF in people with obesity and different GMS.