GDF11 and obesity due to melanocortin 4 receptor deficiency: The main findings of the present study are that 1) serum concentrations of GDF11 peaks at 41-50 y of age progressively declining thereafter with significant decreases observed in the 61-70 and the 71-80 y groups, although this decline seems to have no translation in a reduced FFM; and 2) GDF11 levels showed no gender dimorphism and were unchanged due to obesity or glycemic status.