Final answer:
The liver must be extremely impaired before a clear decrease in protein synthesis is detected, as it is the primary organ responsible for the synthesis of various proteins, including albumin and blood clotting factors.
Step-by-step explanation:
The organ function that must be extremely impaired before an unequivocal decrease in protein synthesis is detected is the liver. The liver plays a crucial role in the synthesis of proteins, including digestive enzymes and plasma proteins like albumin. A significant decrease in these protein levels usually indicates advanced liver dysfunction. Acute liver failure can lead to a decrease in the production of proteins, such as albumin and blood clotting proteins, within a short period from the onset of liver problems. It should be noted that disorders such as protein calorie malnutrition affect all cells in the body, leading to overall slowed growth due to a lack of amino acids for synthetic activities.