Liver performs varying different functions in human body. It is a part of digestive system, endocrine system, excretory system, nutrient metabolism and synthesis, clotting system and body’s defense system against microbes and exogenous toxins.

1. As part of Digestive system: Liver secretes bile which is a digestive juice which helps in digestion of food.
2. As part of Endocrine system (Hormonal System): Liver has many key functions associated with hormones in the body. For example, it is involved in the chemical conversion of thyroid hormone into its most active form. Thyroid hormone is responsible for modulating the body’s metabolic rate (metabolic rate is the the speed at which complex biochemical processes and reactions take place). In addition, it secretes IGF-1, a hormone that promotes cell growth. Angiotensinogen is another hormone produced by the liver. This hormone is part of a complex system that regulates sodium and potassium levels in the kidneys and is involved in blood pressure control. In addition, it regulates hormone levels by breaking down and removing these chemical messengers from the body when they are no longer needed.
3. As part of Excretory System: Liver excretes bilirubin, which is a waste product developed formed during breakdown and recycling of blood cells in body. This substance is excreted along with bile into the intestines and subsequently passes out of the body through faeces.
4. As part of nutrient metabolism, synthesis and detoxification system: Liver is the main seat of major nutrient metabolism in the body. All the digested food is passed through the liver via blood in the portal vein where it is metabolized (broke down into usable form) and stored. Hundreds of metabolic cycles take place and many new chemical substances are synthesized like protein (albumin) and many others. Liver disease adversely effect these metabolic cycles and hence these patients become progressively weak, thin and malnourished.
5. As part of Clotting System: Liver is the main source of production or synthesis of prothrombin (which is a major component of blood clotting system). Is is because of this substance that blood clots whenever there is an injury. In the absence of this substance, a person can even bleed to death. Patients of liver disease (Liver cirrhosis) have problems in blood clotting also.

As part of Defense system microbes and exogenous toxins: Liver acts as a filters for the blood coming from intestines to detoxify the toxins like alcohol and other pathologic substances even drugs and moniter microbial invasion via its kupfer cell system (special cells which captures and kills bacterias and pathological microorganisms).