Hypothyroid and Adrenal Mechanisms
The development of excess body weight in hypothyroidism is linked to a deficiency of iodine-containing thyroid hormones (T3, T4). Under these conditions, metabolic rate and the body's energy expenditure decrease, while lipolysis is inhibited.
In the adrenal (cortisol) mechanism, observed in Cushing's disease or syndrome, the adrenal cortex excessively produces glucocorticoids. This triggers a cascade of abnormalities:
- Gluconeogenesis is activated, leading to hyperglycemia.
- Glucose transport into adipocytes is enhanced.
- Glycolysis is activated in adipose tissue.
- Lipolytic reactions are suppressed, resulting in the accumulation of triglycerides.
Insulin and Leptin Pathways
The endocrine mechanisms of obesity also include the insulin factor. This involves an increased number of insulin receptors and/or their enhanced sensitization. As a result, active lipogenesis is triggered in adipocytes, leading to excessive adipose tissue accumulation.
Significant variants of endocrine pathogenesis include:
- Leptin (adipokine) mechanism
- Hypothyroid mechanism
- Adrenal mechanism
- Insulin mechanism
Role of the Endocannabinoid System
The endocannabinoid system plays a crucial role in regulating the body's energy balance. It closely interacts with the limbic system, the gastrointestinal tract, and adipose tissue.
Normally, cannabinoids participate in metabolic processes, but in obesity, the activity of this system increases, promoting further weight gain.
Metabolic Features and Fat Oxidation
Carbohydrate stores in the human body are extremely small and comparable to daily intake, which evolutionarily established a mechanism for their conservation.
If the proportion of fats in the diet increases, the rate of carbohydrate oxidation naturally decreases. The marker for this process is a decrease in the respiratory quotient—the ratio of carbon dioxide production rate ($CO_2$) to oxygen consumption ($O_2$).
Pathology develops through the following sequence:
- The mechanism inhibiting glycogenolysis is impaired during high blood lipid concentrations.
- The appetite-stimulating center is activated.
- The volume of food consumed increases.
- Excess nutrients are stored as triglycerides.