Key hormones - Insulin
In a previous blog we gave an overview of the Key hormones: insulin, glucagon, testosterone, oestrogen and human growth hormone (HGH). Now we’re taking a more in-depth look at insulin – what it is and what it does.
What does insulin do?
Insulin is a hormone that helps to maintain our blood sugar at the optimum levels.
Where does insulin come from?
Every cell in the body requires energy, which is obtained from the glucose in the food we eat. When glucose enters our bloodstream, the beta cells in the 'Islets of Langerhausen' found within our pancreas secrete insulin, which attaches to other cells and tells them to absorb the glucose.
How does insulin help regulate blood sugar levels?
When our glucose intake is higher than we need, insulin increases the permeability of the liver and muscles cells and stores the glucose as glycogen until it is needed at a later time, for example if we are exercising or haven’t eaten for a while. Glycogen stored in the Liver is called 'Hepatic Glycogen'. When this is broken down back in to glucose during exercise, the glucose enters the blood stream and can be transported anywhere within the body to be used as fuel. Glycogen stored within the muscle can only be used as fuel for that particular muscle. Therefore, the importance of performing large muscle-group exercise to ensure both sources are used / depleted during exercise is very important. Equally, the amount and timings of carbohydrate ingested before and after exercise is also important (Read our blog on: Effects of Protein and Carbohydrate on Resistance Training).
What happens if blood sugar is too high?
High blood sugar (hyperglycemia) is caused when we consume too many calories at once (generally in the form of carbohydrates) and our body cannot efficiently utilise, store and process all the energy in a reasonable time frame resulting in high blood sugar levels. However, high blood sugar levels can also occur following the ingestion of a 'normal' or reasonable amount of carbohydrates. The pancreas produces an insufficient amount of insulin or our cells don’t respond to its effects. This is caused Insulin Resistance or if it has developed to a certain degree of severity, Type 2 Diabetes.
Symptoms include frequent thirst, hunger and need to urinate, tiredness, headaches, blurred vision and weight loss. If left untreated it can lead to more severe symptoms such as vomiting, confusion, abdominal pain and coma.
And too low?
Low blood sugar (hypoglycaemia) can occur but is rare in non diabetics. It usually happens when someone with Type 1 diabetes gets their food intake/exercise and insulin intake out of balance (see our blog on Obesity and diabetes – the effects of a high carb/fat diet).
Symptoms include irritability and anxiety, hunger and trembling, and in severe cases, heart palpitations, dizziness, palpitations and loss of consciousness.
What’s the difference between Type 1 and Type 2 diabetes
In Type 1 diabetes, the beta cells in the pancreas have either been damaged or destroyed, preventing them from secreting insulin and requiring the person to check their blood sugar levels regularly and inject insulin in suitable doses.
Type 2 diabetes develops when beta cells fail and the body doesn’t use insulin efficiently – this can be caused by poor diet. In this case, a change of diet and oral medication can help and even reverse the situation, although the disease can also progress to the subject requiring insulin injections. Exercise and weight loss can also help (see our blog on Personal Training: Diabetes).
Some women develop gestational diabetes as insulin resistance is higher during pregnancy (see our blog on Weight gain during pregnancy).
What types of insulin are used to treat diabetics?
Insulin can be delivered by injection or an insulin pump. There are four different insulin types:
- Rapid-acting insulin – effective after around 15 minutes and usually injected just before a meal
- Short acting insulin – effective after around 30 minutes and usually injected just before a meal
- Intermediate-acting insulin – effective after around two to four hours, usually injected twice a day
- Long-acting insulin – effective after several hours, continues to work for around 24 hours
Different insulin types are usually taken in conjunction with each other, for example a person might take long-acting insulin once a day and boost it with rapid-acting insulin before each meal.
When was insulin first discovered?
After experiments on dogs in 1889, which showed that removing the pancreas gland caused them to develop diabetes, scientists traced the production of the hormone to the pancreas. Sir Edward Albert Sharpey-Shafer gave insulin its name in 1910, based on the Latin word insula (island). In 1921, a team at the University of Toronto removed insulin from the pancreas of a dog and used it to keep another dog alive who had diabetes, and in 1922, a desperately ill boy with diabetes in Toronto, Canada, became the first human to be injected with insulin, bringing his blood sugar levels back down.
What are the latest discoveries about insulin?
A report from UT Health San Antonio released in May 2017 describes how gene transfer has increased the type of cells that can secrete insulin in the pancreas of mice. It is hoped that human clinical trials will start in the next three years.