FNDC5 and type 1 diabetes mellitus: In patients with T1DM, the VAI was independently associated with insulin requirement (total daily insulin U/kg) (p < 0.001, β = 0.666) (Table 2), while in AH circulating irisin levels were independently associated with levothyroxine requirement (p = 0.048, β =  – 0.046) (Table 3).