The human liver can fully regenerate even if 75% of it is surgically removed.

The liver's regenerative capacity is a unique biological phenomenon driven primarily by mature hepatocytes rather than stem cells alone. When tissue is lost, hepatocytes re-enter the cell cycle and replicate until the original mass is restored. This process is regulated by a complex network of growth factors, particularly Hepatocyte Growth Factor (HGF), and cytokines such as Interleukin-6. Research from institutions like the Mayo Clinic confirms that the liver can regain its full weight and functional capacity in as little as 30 days.While ancient mythology referenced this ability—most famously in the story of Prometheus—modern medicine began systematically studying and quantifying liver regeneration in the 20th century. Studies conducted at the University of Pittsburgh Medical Center demonstrate that after a 70% to 75% resection, the remaining liver tissue immediately begins compensatory growth. Rather than regrowing in its original shape, the organ expands its remaining lobes to reach the necessary volume. This hyperplastic response is unique among mammals and does not occur in the heart or lungs.This biological capability forms the foundation for living donor liver transplantation (LDLT). In these procedures, a healthy person donates a portion of their liver to a recipient. Within six to eight weeks, both the donor's remaining liver and the recipient's transplanted segment grow to nearly full size. This process allows one healthy liver to effectively save two lives while ensuring the donor remains healthy with a fully functional organ.