7. TYPICAL DERANGEMENTS OF CARBOHYDRATE METABOLISM. DIABETES MELLITUS

Typical forms of derangement of carbohydrate metabolism include:

• hypoglycemia;

• hyperglycemia;

• glycogenoses;

• aglycogenoses;

• pentosemias-, hexosemias.

HYPOGLYCEMIA

Hypoglycemia may be defined as a decrease of blood glucose below the physiological minimal level of 3,3 mmol/L. Causes of hypoglycemia:

• neurogenic;

• endocrinogenic;

• hepatic;

• renal;

• inadequate substrate supply;

• use of drugs.

Hypoglycemic encephalopathy and coma

In severe cases hypoglycemia typically causes confusion, seizures, stupor, coma, and occasionally hemiparesis or other focal neurological findings. Blood glucose concentrations are typically <1,4 mmol/L (<25 mg/dL). Persistent hypoglycemia depletes cerebral energy supplies and can lead to irreversible neuronal damage. This process has been shown to involve excitotoxic mechanisms in animal studies.

Hypoglycemic encephalopathy is typically caused by accidental or deliberate overdoses of insulin or antidiabetic agents, insulin-secreting islet

cell tumors or retroperitoneal sarcoma, protracted ethanol intoxication (in rare cases), or the Reye's syndrome (in childhood).

HYPERGLYCEMIA

Hyperglycemia is defined as an increase of capillary blood glucose levels above 5.6 mmol/L (or 120 mg/dl). Causes of hyperglycemia:

• neurogenic;

• endocrinogenic;

• alimentary;

• hepatogenic.

GLYCOGENOSES

Glycogenoses are inherited disorders that affect glycogen metabolism. Disorders in virtually every enzyme involved in the synthesis or degradation of glycogen and its regulation cause some type of glycogen storage disease in which glycogen is abnormal in quantity, quality, or both.

Hepatic glycogen storage disease: