Pancreas Applied Physiology
Hypoactivity-Diabetes Mellitus: Diabetes mellitus is a metabolic disorder characterized by high blood sugar (glucose) levels associated with other manifestations. In most cases, the diabetes mellitus develops due to the deficiency of insulin.
Read And Learn More: Medical Physiology Notes
- Types of Diabetes Mellitus: Diabetes mellitus is of two types, Type 1 and Type 2. The differences between the two types are given in Table.
- Type 1 Diabetes Mellitus: It is due to the deficiency of insulin. It occurs because of the dysfunction or absence of p cells in islets of Langerhans. This type of diabetes mellitus is called insulin-dependent diabetes mellitus (IDDM). It is not associated with obesity and may be associated with acidosis or ketosis.
- Type 1 diabetes mellitus may occur at any age of life. But, it usually occurs before 40 years of age. When it. occurs in infancy (due to congenital disorder) or in childhood, it is called juvenile diabetes.
- Causes of type 1 diabetes mellitus
- Degeneration of β cells in the islets of Langerhans of the pancreas
- Destruction of β cells by viral infection
- Congenital disorder of β cells
- Destruction of β cells during autoimmune diseases. It is due to the development of antibodies against β cells.
- Type 2 Diabetes Mellitus: It is due to the absence or deficiency of insulin receptors. It usually occurs after 40 years hence, it is called maturity-onset diabetes mellitus. It may or may not be associated with ketosis. This type of diabetes mellitus is also called noninsulin-dependent diabetes mellitus (NIDDM).
- Causes for type 2 diabetes mellitus: In this type of diabetes the structure and function of β cells and the blood level of insulin are normal. Diabetes develops because of the absence or reduced number of insulin receptors in the cells of the body. The major causes of Type 1 diabetes are:
- Hereditary disorders
- Other endocrine disorders.
- Causes for type 2 diabetes mellitus: In this type of diabetes the structure and function of β cells and the blood level of insulin are normal. Diabetes develops because of the absence or reduced number of insulin receptors in the cells of the body. The major causes of Type 1 diabetes are:
- Type 1 Diabetes Mellitus: It is due to the deficiency of insulin. It occurs because of the dysfunction or absence of p cells in islets of Langerhans. This type of diabetes mellitus is called insulin-dependent diabetes mellitus (IDDM). It is not associated with obesity and may be associated with acidosis or ketosis.
- Diabetes mellitus associated with other endocrine disorders:
- Diabetes is very common in some endocrine disorders like gigantism, acromegaly, and Cushing’s syndrome. Hyperglycemia in these conditions causes excess stimulation of β cells. The constant and excess stimulation, in turn, causes the burning out and degeneration of β cells.
- The β cell exhaustion leads to permanent diabetes mellitus. This type of diabetes mellitus is called secondary diabetes.
- Signs and Symptoms of Diabetes Mellitus: Various manifestations of diabetes mellitus develop because of three major setbacks of insulin deficiency.
- Increased blood sugar level (300-400 mg/dL) due to reduced utilization by tissue
- Mobilization of fats from adipose tissue for energy purposes, leading to elevated fatty acid content in blood. This causes the deposition of fat on the wall of arteries and the development of atherosclerosis
- Depletion of proteins from the tissues.
- Following are the signs and symptoms of diabetes mellitus:
- Glucosuria: Loss of glucose in urine is known as glucosuria. Normally glucose does not appear in the urine. When the glucose level rises above 180 mg/dL in the blood, glucose appears in the urine. It is the renal threshold level for glucose.
- Osmotic diuresis: Diuresis due to osmotic effects is called osmotic diuresis. The excess glucose in the renal tubules develops an osmotic effect. The osmotic effect decreases the reabsorption of water from renal tubules resulting in diuresis. It leads to polyuria and polydipsia.
- Polyuria: Excess urine formation with an increase in the frequency of voiding urine is called polyuria. It is due to the osmotic diuresis caused by an increase in blood sugar level.
- Polydipsia: The increase in water intake is called polydipsia. ILV excess loss of water decreases water content and increases salt content in the body. This stimulates the thirst center in the hypothalamus. The thirst center in turn increases the intake of water.
- Polyphagia: Polyphagia means the intake of excess food. It is very common in diabetes mellitus.
- Asthenia: The loss of strength is called asthenia. The body becomes very weak. There is a loss of energy. Asthenia is because of protein depletion which is caused by a lack of insulin. Lack of insulin causes a decrease in protein synthesis and an increase in protein breakdown resulting in protein depletion. Protein depletion also occurs due to the utilization of proteins for energy in the absence of glucose utilization.
- Acidosis: During insulin deficiency, glucose cannot be utilized by the peripheral tissues for energy. So, a large amount of fat is broken down to release energy. It causes the formation of excess ketoacids leading to acidosis.
- One more reason for acidosis is that the ketoacids are excreted in combination with sodium ions through urine (ketonuria). Sodium is exchanged for hydrogen ions which diffuse from the renal tubules into EOF adding to acidosis.
- Acetone breathing: In cases of severe ketoacidosis, acetone is expired in the expiratory air, giving the characteristic acetone or fruity breath odor. It is a life-threatening condition of severe diabetes.
- Kussmaul breathing: Kussmaul breathing is the increase in rate and depth of respiration caused by severe acidosis.
- Circulatory shock: The osmotic diuresis leads to dehydration, which causes circulatory shock. It occurs only in severe diabetes.
- Coma: Due to Kussmaul’s breathing, a large amount of carbon dioxide is lost during expiration. It leads to drastic induction in the concentration of bicarbonate ions causing Wivere acidosis and coma. It occurs in severe cases of diabetes mellitus.
- An increase in blood sugar level develops hyper-osmolarity of plasma which also leads to coma. It is called a hyperosmolar coma.
- Following are the signs and symptoms of diabetes mellitus:
- Complications of Diabetes Mellitus
- Prolonged hyperglycemia in diabetes mellitus causes dysfunction and injury of many issues resulting in some complications. The development of these complications is directly proportional to the degree and duration of hyperglycemia. However, patients with well-controlled diabetes can postpone the onset or reduce the rate of progression of these complications.
- Initially, untreated chronic hyperglycemia affects the blood vessels resulting in vascular complications like atherosclerosis. Vascular complications are responsible for the development of most of the complications of diabetes such as:
- Cardiovascular complications like:
- Hypertension
- Myocardial infarction
- Degenerative changes in the retina called diabetic retinopathy
- Degenerative changes in kidneys known as diabetic nephropathy
- The degeneration of autonomic and peripheral nerves is called diabetic neuropathy.
- Cardiovascular complications like:
- Diagnostic Tests for Diabetes Mellitus: Diagnosis of diabetes mellitus includes the determination of:
- Fasting blood sugar
- Postprandial blood sugar
- Glucose tolerance test (GTT)
- Glycosylated (glycated) Hb.
- Determination of glycosylated hemoglobin is commonly done to monitor the glycemic control of persons already diagnosed with diabetes mellitus.
- Latent Diabetes: Latent diabetes is the mild form of diabetes mellitus in which the patient does not show overt (observable) symptoms but there is an abnormal response in the diagnostic tests. There is an increased fasting blood sugar level or decreased glucose tolerance.
Functions Of Pancreas
- Treatment for Diabetes Mellitus
- Type 1 diabetes mellitus: Type 1 diabetes mellitus is treated by exogenous insulin. Since insulin is a polypeptide, it is degraded in GL tract if taken orally. So it is generally administered by subcutaneous injection.
- Type 2 diabetes mellitus: Type 2 diabetes mellitus is treated by oral hypoglycemic drugs. Patients with longstanding severe diabetes mellitus may require a combination of oral hypoglycemic drugs with insulin to control the hyperglycemia.
- Oral hypoglycemic drugs are classified into three types.
- Insulin secretagogues: These drugs decrease the blood sugar level by stimulating the secretion of insulin from β cells. Sulfonylureas (tolbutamide, glyburide, glipizide, etc.) are the commonly available insulin secretagogues
- Insulin sensitizers: These drugs decrease the blood sugar level by facilitating insulin action in the target tissues. Examples are biguanides (metformin) and thiazolidinediones (pioglitazone and rosiglitazone)
- Alpha-glucosidase inhibitors: These drugs control blood sugar levels by inhibiting α-glucosidase. This intestinal enzyme is responsible for the conversion of dietary and other complex carbohydrates into glucose and other monosaccharides which can be absorbed from the intestine. Examples of α-glucosidase inhibitors are acarbose and miglitol.
Hyperactivity – Hyperinsulinism: Hyperinsulinism is the hypersecretion of insulin.
- Cause of Hyperinsulinism: Hyperinsulinism occurs due to the tumor of (3 cells in the islets of Langerhans.
- Signs and Symptoms of Hyperinsulinism
- Hypoglycemia: The blood sugar level falls below 50 mg/dL.
- Manifestations of the central nervous system: Manifestations of the central nervous system occur when the blood sugar level decreases. All the manifestations are together called neuroglycopenic symptoms.
Initially, the activity of neurons increases resulting in nervousness, tremors all over the body, and sweating. If not treated immediately, it leads to clonic convulsions and unconsciousness. Slowly, the convulsions cease and coma occurs due to damage of neurons.
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