CDKN2A and hyperinsulinemic hypoglycemia, familial, 4: At a cellular level, aging is associated with accumulation of senescent cells, characterized by an irreversible cell-cycle arrest and increased expression of cyclin-dependent kinase inhibitor 2A (CDKN2A, a.k.a. p16INK4a) [24–26], along with several other biological features such as stem cell exhaustion, systemic klotho deficiency, and telomere attrition [27].