Hormones Involved in Metabolism

Hormones play a crucial role in regulating metabolism, impacting how our bodies use energy. Key players like insulin and glucagon help maintain blood sugar levels, while others like cortisol and thyroid hormones influence overall metabolic processes. Understanding these hormones is essential in Biological Chemistry I.

1. Insulin

   • Produced by the pancreas in response to high blood glucose levels.
   • Facilitates the uptake of glucose into cells, lowering blood sugar levels.
   • Promotes the storage of glucose as glycogen in the liver and muscle tissues.
   • Stimulates fat storage and inhibits fat breakdown.
   • Plays a role in protein synthesis and amino acid uptake.

2. Glucagon

   • Secreted by the pancreas when blood glucose levels are low.
   • Stimulates the liver to convert glycogen back into glucose (glycogenolysis).
   • Promotes gluconeogenesis, the production of glucose from non-carbohydrate sources.
   • Increases blood glucose levels to provide energy during fasting or stress.
   • Works antagonistically to insulin to maintain glucose homeostasis.

3. Epinephrine (Adrenaline)

   • Released from the adrenal glands during stress or "fight-or-flight" situations.
   • Increases blood glucose levels by promoting glycogenolysis and gluconeogenesis.
   • Enhances lipolysis, the breakdown of fats for energy.
   • Increases heart rate and blood flow to muscles, preparing the body for rapid action.
   • Plays a role in the regulation of metabolic processes during acute stress.

4. Cortisol

   • A steroid hormone produced by the adrenal cortex in response to stress.
   • Increases blood glucose levels by promoting gluconeogenesis and inhibiting glucose uptake in non-essential tissues.
   • Affects protein metabolism by promoting protein breakdown for energy.
   • Regulates fat metabolism and can lead to increased fat storage.
   • Plays a role in the body's response to chronic stress and inflammation.

5. Thyroid hormones (T3 and T4)

   • Produced by the thyroid gland, these hormones regulate metabolism and energy expenditure.
   • Increase the basal metabolic rate (BMR), influencing how quickly the body uses energy.
   • Affect protein synthesis and the metabolism of carbohydrates and fats.
   • Essential for normal growth and development, particularly in children.
   • Influence the sensitivity of tissues to other hormones, including insulin.

6. Growth hormone

   • Secreted by the pituitary gland, it stimulates growth and cell reproduction.
   • Increases protein synthesis and promotes the utilization of fat for energy.
   • Plays a role in maintaining blood glucose levels by reducing glucose uptake in muscle and fat tissues.
   • Influences the growth of bones and muscle mass.
   • Affects metabolism by promoting the breakdown of fats and the conservation of glucose.

7. Leptin

   • Produced by adipose (fat) tissue, it signals satiety and regulates energy balance.
   • Informs the brain about fat stores, influencing appetite and energy expenditure.
   • High levels of leptin suppress appetite, while low levels stimulate hunger.
   • Plays a role in regulating metabolism and the body's response to energy deficits.
   • Implicated in obesity, as resistance to leptin can lead to overeating.

8. Ghrelin

   • Known as the "hunger hormone," it is produced in the stomach and stimulates appetite.
   • Levels increase before meals and decrease after eating, signaling hunger to the brain.
   • Plays a role in energy balance and fat storage.
   • Influences the release of growth hormone from the pituitary gland.
   • May affect metabolism by promoting fat storage and reducing energy expenditure.

9. Glucagon-like peptide-1 (GLP-1)

   • An incretin hormone released from the intestines in response to food intake.
   • Enhances insulin secretion from the pancreas in a glucose-dependent manner.
   • Inhibits glucagon release, reducing blood glucose levels.
   • Slows gastric emptying, promoting a feeling of fullness.
   • Plays a role in glucose homeostasis and appetite regulation.

10. Adiponectin

    • Secreted by adipose tissue, it enhances insulin sensitivity and regulates glucose levels.
    • Involved in the metabolism of lipids and glucose, promoting fat oxidation.
    • Higher levels are associated with lower risk of obesity-related diseases.
    • Plays a role in anti-inflammatory processes and cardiovascular health.
    • Its levels are inversely related to body fat percentage; lower in obese individuals.