Insulin: Hormone Functions, Types, Norm

2024 Author: Rachel Wainwright | [email protected]. Last modified: 2023-12-15 07:39

Insulin: hormone functions, types, norm

The content of the article:

1. Insulin functions
2. Diseases associated with the action of insulin

3. Insulin therapy

   1. Combined (traditional) insulin therapy
   2. Intensified insulin therapy
4. Insulin types
5. Commercial insulin preparations

Insulin is a protein synthesized by β-cells of the pancreas and consists of two peptide chains linked by disulfide bridges. It provides a decrease in the concentration of glucose in the blood serum, taking a direct part in carbohydrate metabolism.

Indicators of the norm of insulin in the blood serum of a healthy adult lie in the range from 3 to 30 μU / ml (after 60 years - up to 35 μU / ml, in children - up to 20 μU / ml).

Insulin levels in the blood are determined using a blood test

The following conditions lead to a change in the concentration of insulin in the blood:

• diabetes;
• muscular dystrophy;
• chronic infections;
• acromegaly;
• hypopituitarism;
• exhaustion of the nervous system;
• liver damage;
• malnutrition with an excessively high content of carbohydrates in the diet;
• obesity;
• hypodynamia;
• physical overwork;
• malignant neoplasms.

Insulin functions

The pancreas has areas of β-cell congestion called the islets of Langerhans. These cells produce insulin around the clock. After eating, the concentration of glucose in the blood rises, in response to this, the secretory activity of β-cells increases.

The main action of insulin is to interact with cytoplasmic membranes, resulting in an increase in their permeability to glucose. Without this hormone, glucose could not penetrate into the cells, and they would experience energy starvation.

In addition, insulin performs a number of other equally important functions in the human body:

• stimulating the synthesis of fatty acids and glycogen in the liver;
• stimulating the absorption of amino acids by muscle cells, due to which there is an increase in the synthesis of glycogen and protein in them;
• stimulating the synthesis of glycerol in lipid tissue;
• suppression of the formation of ketone bodies;
• suppression of lipid breakdown;
• suppression of the breakdown of glycogen and proteins in muscle tissue.

Thus, insulin regulates not only carbohydrate metabolism, but also other types of metabolism.

Diseases associated with the action of insulin

Both insufficient and excessive concentrations of insulin in the blood cause the development of pathological conditions:

• insulinoma - a tumor of the pancreas that secretes a large amount of insulin, as a result of which the patient often develops hypoglycemic conditions (characterized by a decrease in serum glucose concentration below 5.5 mmol / l);
• type I diabetes mellitus (insulin-dependent type) - its development is caused by insufficient production of insulin by β-cells of the pancreas (absolute insulin deficiency);
• type II diabetes mellitus (insulin-independent type) - the cells of the pancreas produce insulin in sufficient quantities, but the receptors of the cells lose their sensitivity to it (relative insufficiency);
• insulin shock is a pathological condition that develops as a result of a single injection of an excessive dose of insulin (in a severe form, hypoglycemic coma);
• Somoji syndrome (chronic insulin overdose syndrome) is a complex of symptoms that occur in patients receiving high doses of insulin for a long time.

Insulin therapy

Insulin therapy is a method of treatment aimed at eliminating disorders of carbohydrate metabolism and based on the injection of insulin preparations. It is mainly used in the treatment of type I diabetes mellitus, and in some cases also for type II diabetes mellitus. Very rarely, insulin therapy is used in psychiatric practice, as one of the methods of treating schizophrenia (treatment of hypoglycemic coma).

Indications for insulin therapy are:

• type I diabetes mellitus;
• diabetic hyperosmolar, hyperlaccidemic coma, ketoacidosis;
• inability to achieve compensation of carbohydrate metabolism in patients with type II diabetes mellitus with hypoglycemic drugs, diet and dosed physical activity;
• gestational diabetes mellitus;
• diabetic nephropathy.

The injections are given subcutaneously. They are performed using a special insulin syringe, pen syringe or insulin pump. In Russia and the CIS countries, most patients prefer to inject insulin using pen-syringes, which ensure accurate dosage of the drug and virtually painless administration.

Insulin is injected subcutaneously with a special insulin syringe

Insulin pumps are used by no more than 5% of patients with diabetes. This is due to the high cost of the pump and the complexity of its use. Nevertheless, the introduction of insulin using a pump provides an accurate imitation of its natural secretion, provides better glycemic control, and reduces the risk of developing short and long-term consequences of diabetes mellitus. Therefore, the number of patients using dosing pumps for the treatment of diabetes mellitus is steadily increasing.

In clinical practice, different types of insulin therapy are used.

Combined (traditional) insulin therapy

This method of diabetes mellitus therapy is based on the simultaneous administration of a mixture of short and long-acting insulins, which reduces the daily number of injections.

The advantages of this method:

• there is no need for frequent monitoring of blood glucose concentration;
• therapy can be carried out under the control of urinary glucose levels (glucosuric profile).

Main disadvantages:

• the need for strict adherence to the daily regimen, physical activity;
• the need for strict adherence to the diet prescribed by the doctor, taking into account the administered dose;
• the need to eat at least 5 times a day and always at the same time.

Traditional insulin therapy is always accompanied by hyperinsulinemia, that is, increased insulin levels in the blood. This increases the risk of developing complications such as atherosclerosis, arterial hypertension, hypokalemia.

Basically, traditional insulin therapy is prescribed to the following categories of patients:

• elderly;
• suffering from mental illness;
• with a low educational level;
• in need of outside care;
• unable to comply with the doctor's recommended daily regimen, diet, timing of insulin administration.

Intensified insulin therapy

Intensified insulin therapy mimics the physiological secretion of insulin in the patient's body.

In order to simulate basal secretion in the morning and evening, prolonged types of insulin are administered. After each meal containing carbohydrates, short-acting insulin is administered (imitation of post-meal secretion). The dose is constantly changing depending on the food consumed.

The advantages of this method of insulin therapy are:

• imitation of the physiological rhythm of secretion;
• higher quality of life for patients;
• the ability to adhere to a more liberal daily regimen and diet;
• reducing the risk of developing late complications of diabetes.

The disadvantages include:

• the need to educate patients in the calculation of XE (bread units) and the correct selection of the dose;
• the need to exercise self-control at least 5-7 times a day;
• an increased tendency to develop hypoglycemic conditions (especially in the first months of the appointment of therapy).

Insulin types

Insulin happens:

• one-species (monospecific) - are an extract of the pancreas of one species of animals;
• combined - contains in its composition a mixture of extracts of the pancreas of two or more species of animals.

By species:

• human;
• pork;
• cattle;
• whale.

There are different insulin preparations, differing in speed and duration of action and in origin.

Depending on the degree of purification, insulin is:

• traditional - contains impurities and other hormones of the pancreas;
• monopik - due to additional filtration on the gel, the content of impurities in it is much less than in the traditional one;
• mono - component - has a high degree of purity (contains no more than 1% impurities).

According to the duration and peak of action, insulins of short and prolonged (medium, long and ultra-long) action are isolated.

Commercial insulin preparations

The following types of insulin are used to treat patients with diabetes mellitus:

1. Simple insulin. It is represented by the following drugs: Actrapid MC (porcine, monocomponent), Actrapid MP (porcine, monopic), Actrapid HM (genetically engineered), Insuman Rapid HM and Humulin Regular (genetically engineered). Begins to act 15-20 minutes after injection. The maximum effect is noted in 1.5-3 hours from the moment of injection, the total duration of action is 6-8 hours.
2. NPH insulins or long acting insulins … Earlier in the USSR, they were called protamine-zinc-insulins (PCI). Initially, they were prescribed once a day to mimic basal secretion, and short-acting insulins were used to compensate for the rise in blood glucose after breakfast and dinner. However, the effectiveness of this method for correcting disorders of carbohydrate metabolism turned out to be insufficient, and at present, manufacturers are preparing ready-made mixtures using NPH-insulin, which can reduce the number of insulin injections to two per day. After subcutaneous administration, the effect of NPH insulin begins after 2–4 hours, reaches a maximum after 6–10 hours, and lasts 16–18 hours. This type of insulin is presented on the market by the following drugs: Insuman Basal, Humulin NPH, Protaphane HM, Protaphane MC, Protaphane MP.
3. Ready-made fixed (stable) mixtures of NPH and short-acting insulin. Injected subcutaneously twice a day. Not suitable for all patients with diabetes. In Russia, there is only one stable ready-made mixture of Humulin M3, which contains 30% Humulin Regular short insulin and 70% Humulin NPH. This ratio is less likely to provoke the occurrence of hyper- or hypoglycemia.
4. Super long-acting insulins. They are used only for the treatment of patients with type II diabetes mellitus who need a constant high concentration of insulin in the blood serum due to the resistance (resistance) of tissues to it. These include: Ultratard HM, Humulin U, Ultralente. The action of ultra-long-term insulins begins 6-8 hours from the moment of their subcutaneous injection. Its maximum is reached after 16–20 hours, and the total duration of action is 24–36 hours.
5. Genetically engineered short-acting human insulin analogs (Humalog). They begin to act within 10-20 minutes after subcutaneous administration. The peak is reached in 30–90 minutes, the total duration of action is 3–5 hours.
6. Peakless (long-acting) human insulin analogs. Their therapeutic effect is based on blocking the synthesis of the hormone glucagon, which is an insulin antagonist, by the alpha cells of the pancreas. The duration of action is 24 hours, there is no peak concentration. Representatives of this group of drugs are Lantus, Levemir.

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Elena Minkina Doctor anesthesiologist-resuscitator About the author

Education: graduated from the Tashkent State Medical Institute, specializing in general medicine in 1991. Repeatedly passed refresher courses.

Work experience: anesthesiologist-resuscitator of the city maternity complex, resuscitator of the hemodialysis department.

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