FNDC5 and hydrops fetalis: Like other investigators, we did not find a strong correlation between irisin and metabolic parameters, including the HOMA index in T2DM with known HF (Abd El-Mottaleb et al., 2019; Silvestrini et al., 2019), but a weak inverse correlation of the biomarker with BMI, WHR and NT-proBNP was observed.