Mechanisms of hyperglycemia development
The pathogenesis is based on insulin deficiency, which triggers a cascade of severe metabolic disorders. Anabolic processes in the body sharply decline, while the level of counter-regulatory hormones (which include glucagon, cortisol, growth hormone, and catecholamines), conversely, increases significantly.
Such hormonal imbalance leads to a total dominance of catabolism. The processes of breakdown and synthesis are activated in the liver and tissues:
- Glycogenolysis (breakdown of glycogen stores).
- Gluconeogenesis (formation of new glucose from non-carbohydrate components).
- Lipolysis (breakdown of fats).
As a result of these processes, blood glucose levels rapidly increase. An important role is played by excess cortisol, which exerts a pronounced counter-regulatory effect — it not only stimulates gluconeogenesis but also reduces the sensitivity of peripheral tissues to insulin, which can lead to the development of so-called steroid diabetes mellitus.
Pathogenesis of clinical manifestations
High blood glucose concentrations have systemic pathogenetic consequences. The clinical picture is formed due to the disruption of all types of metabolism: carbohydrate, lipid, protein, and mineral.
The classical triad of symptoms includes:
- Polyuria (pathological increase in urine volume).
- Polydipsia (unquenchable thirst).
- Polyphagia (pathologically increased appetite).
An increase in glucose levels above the renal threshold causes glucosuria, which is inevitably followed by osmotic diuresis. The body rapidly loses fluid, and dehydration develops. Against the background of active lipolysis, hyperketonemia occurs (accumulation of ketone bodies), which shifts the acid-base balance toward acidosis. The extreme degree of this process is life-threatening diabetic ketoacidosis.
General energy and insulin deficiency manifest as marked weakness, exhaustion, weight loss, tachycardia, and arterial hypotension. Patients frequently develop specific inflammatory processes of the mucous membranes (vulvitis, balanitis). In severe courses, pulmonary hyperventilation, peripheral vasodilation, and hypothermia are observed.
Systemic impact on organs and tissues
Chronic hyperglycemia provokes chronic hypoxia and cellular energy starvation. Over time, this leads to damage, dysfunction, and failure of vital organs: the eyes, kidneys, nerves, heart, and blood vessels.
Additional clinical syndromes are often caused by the concomitant effects of excess hormones (for example, cortisol and aldosterone):
- Arterial hypertension develops due to increased cardiac output, elevated arteriolar wall tone, and an increase in circulating blood volume (CBV).
- Muscle weakness and hypodynamia develop due to dystrophic changes, reduced glucose uptake into myocytes, and ion imbalance (accumulation of intracellular sodium $Na^+$ and loss of potassium $K^+$).
- Osteoporosis occurs as a result of the inhibition of collagen synthesis in bones, impaired absorption of calcium ions $Ca^{2+}$ in the intestine, and its mobilization from bone tissue.
The classical triad of hyperglycemia symptoms in diabetes is easily remembered as the "Rule of Three P's": Polyuria, Polydipsia, Polyphagia.
Class and exam questions
What is the main cause of hyperglycemia in diabetes mellitus?
The main cause is absolute or relative hypoinsulinism, in which insulin secretion is impaired or tissue sensitivity to its action is reduced (insulin resistance).
Why does pronounced muscle weakness occur in hyperglycemia?
Weakness is associated with decreased glucose levels in myocytes, dystrophic changes in muscle tissue, and ion imbalance (accumulation of sodium and loss of potassium inside cells).
How does cortisol affect blood glucose levels?
Excess cortisol has a counter-regulatory effect. It actively stimulates gluconeogenesis in the liver while simultaneously reducing the sensitivity of peripheral tissues to insulin.
What else to study on this topic
- Pathogenesis of diabetic ketoacidosis and hyperketonemia.
- Acute complications of diabetes mellitus (hyperosmolar state, lactic acidosis).
- Mechanisms of steroid osteoporosis formation in excess cortisol.
- The role of hypoxia in target organ damage in diabetes mellitus.
- Contraindications to vaccination in acute hyperglycemic states.
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