by Hannah Farrell
What are the functions of the liver?
The liver is a large organ located under the diaphragm on the right side of the abdomen. It has two main functions:
- Storage: carbohydrates, vitamins A, D, E, K, and B12, and iron.
- Metabolism: carbohydrate, lipid, protein, ammonia, and vitamin metabolism, and detoxification including the metabolism of medications and alcohol.
Further information on liver function can be found here.
Carbohydrate Metabolism
The liver metabolises excess glucose upon stimulation from insulin (released from the pancreas), storing it as glycogen. The stored glycogen is then broken down into glucose when the body requires it. Upon stimulation from cortisol and glucagon, the liver is also able to convert other substances into glucose through a process known as gluconeogenesis.
Lipid Metabolism
The liver cells will begin a process called lipogenesis when stimulated by insulin. Lipogenesis leads to the production of lipids (fats). Lipogenesis is inhibited by adrenaline and glucagon. The liver also manages the breakdown of fats (lipolysis) when stimulated by glucagon and adrenaline.
Protein Metabolism
The liver produces a variety of important proteins, including:
- Albumin – a protein that prevents fluid from escaping blood vessels and aids with transporting substances (such as medicines) in the bloodstream.
- C-reactive protein (CRP) – a marker of inflammation.
- Clotting Factors – proteins produced to help the blood clot.
- Thrombopoietin – a hormone that stimulates platelet production.
- Angiotensinogen – a major component in blood pressure and fluid regulation.
The liver is also responsible for metabolising excess proteins, which leads to the production of ammonia, which is excreted in the urine.
Ammonia Metabolism
As ammonia is toxic to the body, it is important that it is metabolised and excreted from the body. The liver can use ammonia to create glutamine, which is used to produce components of DNA. Alternatively, the liver converts ammonia to urea, which is excreted in urine.
Vitamin Metabolism
- Vitamin D – the liver plays a major role in activating vitamin D, ready to be converted by the kidney to a biologically active form of vitamin D (controlled by parathyroid hormone).
- Vitamin A – the liver produces bile which aids in the absorption of vitamin A from the intestines. The liver also produces a protein responsible for distributing vitamin A to the peripheral tissues. The liver is also stores the largest volume of vitamin A in the body.
- Vitamin K – the liver reduces vitamin K to a form which activates clotting factors II, VII, IX, X, and protein C and S (responsible for blood clotting).
- Vitamin B12 – this is stored in the liver.
What is Hepatitis?
Hepatitis is inflammation of the liver. The liver can become inflamed for a variety of reasons and may be acute or chronic. Hepatitis is categorised as below:
- Viral:
- Hepatitis A – spread through faeces
- Hepatitis B – spread through blood and body fluids
- Hepatitis C – spread through blood and body fluids
- Hepatitis D – spread through blood and body fluids, only affecting individuals who have previously been infected with hepatitis B
- Hepatitis E – spread through faeces
- Other viruses e.g., Epstein Barr virus
- Hepatitis from toxins:
- Alcoholic hepatitis
- Medication induced
- Excess iron e.g., haemochromatosis
- Excess copper e.g., Wilson’s disease
- Autoimmune hepatitis
Several types of hepatitis will have very little long-term impact on the individual, however other types are more damaging with greater consequences such as liver cirrhosis, liver cancer, and impaired liver function.
Symptoms of hepatitis reflect the disturbed function of the liver and include:
- Dark urine
- High temperature
- Nausea and vomiting
- Aches and pains
- Fatigue
- Abdominal pain, particularly on the right side
- Pale faeces
- Itching
- Jaundice
Treatment of hepatitis depends on which type it is and the severity of symptoms. Options include antiviral agents, immunosuppression medications, and in extreme cases liver transplantation.
Our expert witnesses in hepato-pancreato-biliary (HPB) surgery specialise in the management of disorders affecting the liver, pancreas, and biliary tract; they have a special interest in hepatitis.