The subgroup of ALL survivors meeting the metabolic criterion for a diagnosis of insulin resistance (10.7%) showed higher levels of C-peptide (1150.13 ± 626.88 pg/mL vs. 425.84 ± 528.95 pg/mL, p = 0.005), glucagon (625.22 ± 355.41 pg/mL vs. 284.69 ± 177.93 pg/mL, p = 0.042), and leptin (9930.65 ± 6458.18 pg/mL vs. 2906.16 ± 4843.62 pg/mL, p = 0.016) in comparison to subjects with normal HOMA-IR. The gene discussed is LEP; the disease is acute lymphoblastic leukemia.