Chapter 4: Glucose Metabolism

Chapter 4: Glucose Metabolism

# Role of the Pituitary Gland in Blood Glucose Regulation

The anterior pituitary gland plays a significant role in blood glucose regulation. Specifically:

• Decreased glycogen synthesis and increased glycogen breakdown: The anterior pituitary gland reduces the amount of glycogen stored in the body while simultaneously stimulating the breakdown of glycogen into glucose, leading to increased blood sugar levels.

• Reduced glucose permeability into tissues: The anterior pituitary gland decreases the ability of tissues to absorb glucose, contributing to elevated blood sugar levels.

# Role of ACTH in Glucose Metabolism

ACTH (anterior pituitary hormone) stimulates the adrenal cortex to secrete steroid hormones, including glucocorticoids. Glucocorticoids have an impact on glucose metabolism:

• Increased blood glucose: Glucocorticoids increase glucose production from the liver while simultaneously reducing peripheral glucose utilization, leading to increased blood sugar levels.

• Increased protein breakdown: Glucocorticoids increase protein breakdown, releasing amino acids into the bloodstream. A portion of these amino acids is used for glucose synthesis in the liver, contributing to increased blood sugar levels.

# Disorders of Glucose Metabolism

9.1 Diabetes Mellitus

Diabetes mellitus is a common disease associated with impaired insulin production or utilization. Insulin is a hormone secreted by beta cells of the islets of Langerhans in the pancreas, playing a crucial role in blood glucose regulation.

There are two types of diabetes mellitus:

• Type 1: Also known as juvenile diabetes or insulin-dependent diabetes. This type usually occurs in children and young adults, caused by the body’s immune system attacking and destroying beta cells of the islets of Langerhans, leading to insulin deficiency. The primary treatment method is insulin supplementation.

• Type 2: Also known as adult-onset diabetes or non-insulin-dependent diabetes. This type typically occurs in older adults, due to the body’s inability to respond to insulin or insufficient insulin production. The exact cause of type 2 diabetes is not fully understood, but it may be related to genetics, diet, and lifestyle. Treatment includes dietary modifications, exercise, and medication.

Characteristics of individuals with diabetes mellitus:

• Elevated blood glucose levels: Due to insulin deficiency, glucose cannot be effectively transported into cells, leading to increased blood glucose levels.

• Increased ketone bodies and free fatty acids in the blood: When the body cannot use glucose as its primary energy source, it turns to fat. This process produces ketone bodies and free fatty acids, increasing their concentration in the blood.

• Salt loss: Due to increased glucose excretion in urine, the body also loses a certain amount of salt.

• Increased urine volume, urea: Excess glucose in the blood is excreted through urine, increasing urine volume and urea concentration.

• Tissue and cell energy deprivation: Due to the inability of cells to utilize glucose, they experience energy deficiency, leading to functional disturbances.

Causes of diabetes mellitus:

• Insulin deficiency: Insulin deficiency reduces the ability of glucose to transport across cell membranes, resulting in excess glucose in the blood and cell energy deprivation.

• Enhanced lipid catabolism: The body increases its utilization of fat for energy production, leading to increased free fatty acids in the blood and ketone body production.

• Lipid metabolism disorder: Enhanced lipid catabolism, coupled with insulin deficiency, causes lipid metabolism disorders, affecting the entire body.

• Water and salt metabolism disorder: Increased glucose excretion in urine leads to water and salt loss, resulting in electrolyte imbalance.

Consequences of diabetes mellitus:

• Organ dysfunction: Prolonged energy deficiency can cause dysfunction of organs in the body, such as cataracts, damage to the vascular system, weakened immune system, and infections.

9.3 Classic Galactosemia

Classic galactosemia is a rare genetic disorder caused by a deficiency of the enzyme galactose-1-phosphate uridyl transferase. This enzyme plays a crucial role in converting galactose to glucose. Its deficiency leads to galactose accumulation in the liver, causing liver failure, which can be fatal.

Treatment:

• Discontinue breastfeeding: Because breast milk contains a high amount of lactose, it’s necessary to stop breastfeeding and replace it with lactose-free formula.

Conclusion:

Glucose metabolism is a vital process in the body, ensuring energy supply for life activities. Disorders of glucose metabolism, especially diabetes mellitus, can lead to numerous dangerous complications. Treatment and blood sugar control are essential for maintaining health and quality of life.