Diabetes mellitus

Mechanism of pathological development

The pathogenetic basis of diabetes mellitus development is that hyperglycemia occurs due to two global causes, which can manifest either isolated or in combination:

• Insulin secretion defect. The pancreas produces an insufficient amount of the hormone (absolute or relative insufficiency).
• Impaired insulin action. Target cells lose sensitivity to the hormone (insulin resistance).

If the insulin link fails due to impaired production or tissue insensitivity, glucose cannot physically penetrate into the cells. It remains in the bloodstream, causing chronic hyperglycemia. This very process is the basic symptom of absolutely any carbohydrate metabolism disorders.

Physiological regulation of carbohydrate metabolism

For a deep understanding of the pathogenesis of diabetes mellitus, it is necessary to know the normal range of glycemia fluctuations. This physiological process directly depends on food intake.

Postprandial period (the state after food intake)

The absorption of carbohydrates from the gastrointestinal tract leads to a natural alimentary increase in blood glucose levels. In response to this stimulus, the pancreas promptly increases insulin secretion.

The effects of insulin are multifaceted:

1. It stimulates glucose uptake by peripheral tissues.
2. It triggers the synthesis of the storage carbohydrate—glycogen in the liver and muscles (glycogenogenesis).

As a result of these actions, the glycemic level successfully returns to the physiological norm.

Fast state

In the absence of food, blood glucose levels physiologically decrease, and insulin secretion predictably drops to a basal (very low) level. To prevent critical energy deficiency, the body activates the release of counter-regulatory hormones: glucagon, growth hormone (GH), cortisol, and adrenaline.

These hormones prevent blood sugar from dropping critically by triggering three crucial compensatory mechanisms:

• Glycogenolysis — the breakdown of previously stored glycogen into free glucose.
• Gluconeogenesis — the synthesis of glucose molecules from non-carbohydrate substrates.
• Lipolysis — the breakdown of fats to provide the body with alternative energy.

General classification of diabetes mellitus

The study of diabetes mellitus logically continues with an analysis of its classification, detailed pathogenesis, and etiological factors. Modern medical classification distinguishes four main groups of carbohydrate metabolism disorders:

1. Type 1 DM. This group includes autoimmune pathologies, as well as the idiopathic variant of the disease course.
2. Type 2 DM. The most common form, closely associated with insulin resistance.
3. Gestational DM. A specific form of diabetes that first occurs and is diagnosed during pregnancy.
4. Other specific types of DM. A rather extensive miscellaneous group. It includes various genetic anomalies, as well as secondary diabetes developing against the background of other pathologies and external influences.

Class and exam questions

What else to study on this topic

• Etiological factors and pathogenesis of type 1 diabetes mellitus (autoimmune and idiopathic variants)
• Mechanisms of insulin resistance development in type 2 diabetes mellitus
• Genetic anomalies and secondary pathologies in the group of "other specific types of DM"
• Features of the clinical course and diagnosis of gestational diabetes mellitus

Other topics in the section «Chapter 11. Endocrine Diseases in Children»

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.