Monitoring the level of some proteins, such as the increase of CTSD, GDF15, GUSB, MCFD2, REG1A, REG1B, and TCN2 and concomitantly the decrease of FABP4, LEP, and LPL may help in identifying the group of patients with obesity with higher risk for the appearance of T2D allowing for more precise therapeutic interventions. The gene discussed is TCN2; the disease is obesity due to melanocortin 4 receptor deficiency.