Which substance accounts for a majority of bilirubin production in infants?

Bilirubin is a byproduct of the breakdown of hemoglobin, which is found in red blood cells. In infants, particularly those who are premature or have certain conditions, the production of bilirubin can increase due to the rapid turnover of red blood cells as the body clears out excess fetal red blood cells after birth. Hemoglobin is the primary component responsible for this process, making it the main source of bilirubin production in infants. The liver then processes this bilirubin, conjugating it to make it water-soluble for excretion.

Fibrinogen, myoglobin, and albumin do not play a direct role in bilirubin production. Fibrinogen is involved in blood clotting, myoglobin is found in muscle tissues and helps store oxygen, while albumin is primarily a protein in the blood that maintains oncotic pressure and transports various substances. Therefore, the majority of bilirubin production in infants is attributed to the breakdown of hemoglobin.