What Is Insulin and What Does It Do To the Body? Diabetes

What Is Insulin?

Insulin is a hormone (a chemical substance that acts as a messenger in the human body) that is secreted by an abdominal organ called the pancreas. It is a "key" that unlocks the cell gates so that glucose from the blood enters the cells. Only then can the cells utilize this glucose as a fuel for their functions.

Glucose is the primary fuel for most body cells. The muscles and fatty tissue are especially dependent on insulin for glucose uptake and use. The lack of insulin in the body or inefficient action of insulin at the cellular levels can cause the blood sugar levels to spike (hyperglycemia). Hyperglycemia is the hallmark of diabetes mellitus.

Hyperglycemia is dangerous. Despite high blood sugar levels, the cells are deprived of their fuel and cannot function. High blood sugar levels cause swelling in the brain cells resulting in disturbed brain function that may progress to coma. Persistent high glucose levels damage the inner lining of the blood vessels and nerve fibers and increase the risk of heart attack, stroke, kidney failure, and vision loss.

Insulin is the only hormone in the body that can prevent hyperglycemia. It counterbalances the effects of other hormones such as glucagon, epinephrine, growth hormone, and cortisol that increase blood sugar levels.

What Does Insulin Do to the Body?

Insulin is released in spurts when we eat. It helps the body maintain normal blood sugar levels. Glucose values in a fasting state (not eating or drinking anything except water for at least 8 hours before the test) and 2 hours after a meal (postprandial) are given in the tables below:

Fasting Blood Glucose:

Normal	Less than 100 mg/dL
Pre-diabetes	100-125 mg/dL
Diabetes	126 mg/dL or higher

Postprandial Blood Glucose:

Normal	Less than 140 mg/dL
Pre-diabetes	140-199 mg/dL
Diabetes	200 mg/dL or higher

Additionally, insulin helps the body breakdown food into energy. These are all metabolic functions of insulin.

Sr. No	Organs	Action of insulin
1.	Muscle	Glucose from the blood can enter the muscle cells only in the presence of insulin. Insulin increases the protein content in the muscles to prevent muscle wasting.
2.	Liver	It helps convert glucose to a storage product called "glycogen." Glycogen is an energy source when you are in a fasting state. It causes increased fat synthesis and slows the breakdown of fats. It directs the liver to use carbs as energy fuel in place of fats. It is useful in the increased synthesis of proteins.
3.	Adipose (fatty tissue)	It helps in the reduced breakdown of fats to free fatty acids.
4.	Body cells	It helps the entry of potassium inside the body cells that are required for proper cell functions.
5.	Brain	It regulates our feeding behavior. It protects against dementia and Alzheimer's disease.
6.	KIdney	It helps in the excretion of sodium out of the body through urine.
7.	Bone	It stimulates bone formation and suppresses bone breakdown.

What Is Diabetes Mellitus?

Diabetes mellitus is a metabolic disease characterized by constantly high blood sugar levels. The American Diabetes Association (ADA) criteria for diagnosing diabetes are as follows:

Fasting blood sugar levels more than 126 mg/dL
Post-meal blood sugar levels more than 200 mg/dL
A random sugar reading of or above 200 mg/dL along with the symptoms of diabetes

Depending on the pathology of the disease, diabetes mellitus can be of two main types:

Type I Diabetes Mellitus	Type II Diabetes Mellitus
It is characterized by insulin deficiency (the absence of insulin in the body).	In this, insulin is present, but the muscle and fatty tissue do not adequately respond to the available insulin (insulin resistance).
It is characterized by insulin deficiency (the absence of insulin in the body). It is mostly seen in young adults or children.	It is mostly seen in middle-aged people.
It is characterized by insulin deficiency (the absence of insulin in the body). It is mostly seen in young adults or children.	Its causes include: Obesity Poor eating habits Lack of exercise Genetics
It can only be treated by insulin shots.	It can be managed by insulin, drugs, and lifestyle changes.
In this, there is a high risk of diabetic ketoacidosis (diabetic coma).	In this, there is a low risk of diabetic ketoacidosis.

How Is Insulin Given In Case of Diabetes?

Insulin is a mainstay of therapy in the following cases of diabetes:

Type I diabetes
Type II diabetes not responding to oral medications
Autoimmune diabetes
Diabetes of pregnancy

Long-acting insulins, short-acting insulins, regular insulins, and mixed insulin are several types of insulin available in the market. The American Diabetes Association (ADA) has issued guidelines on which type is the best suited for your situation.

Injections	Pump	Inhaled
Insulin is injected subcutaneously (below your skin) with a special pen or syringe.	An insulin pump is fixed to your belly, and it dispenses insulin into your blood as and when you press the button or as programmed.	You breathe a fine insulin powder with the help of an inhaler.
Depending on your sugar levels, single or multiple shots of insulin may be needed before meals or before sleeping.	The pump has a sensor that senses your blood sugar level and delivers the required dose during meals. It also delivers a baseline insulin dose throughout the day to maintain steady blood sugar levels.	It is to be taken before meals.
You may be prescribed rapid-acting, mixed, or slow-acting insulin depending on your sugar levels.	Generally, the pump uses only regular or rapid-acting insulins.	It cannot be used in a diabetic coma.

From

Diabetes Resources

How Diabetes Affects Vision

Featured Centers

References

References:

https://teachmephysiology.com/endocrine-system/pancreas/insulin/
https://care.diabetesjournals.org/content/13/6/655
https://www.diabetes.org/a1c/diagnosis