Endo IV Flashcards
What is Addison’s disease? What is its cause?
- Characterized by failure of adrenal cortex to produce adrenocortical hormones (hypofunction)
- May involve total destruction of the gland
- Mostly due to atrophy of the adrenal glands due to tuberculosis and involves medulla as well as cortex
How does Addison’s disease affect glucocorticoid production? Explain the consequences on the body.
Glucocorticoid deficiency leads to:
- Decreased blood sugar (particularly between meals)
- Decreased lipolysis
- Decreased gluconeogenesis
- Lack of energy, muscular weakness, inability to take stress
How does Addison’s disease affect mineralocorticoid production? Explain the consequences on the body.
- Plasma: decreased Na+, Cl-, and H2O - all lost in urine
- Leads to decreased extracellular fluid, plasma volume, and cardiac output
- Increased K+ (hyperkalemia), H+ (acidosis) - reabsorbed from urine
- Patient dies in shock 7 days after complete absence of mineralocorticoids
What is Cushing’s disease? What is its cause?
- Characterized by the hyperplasia of the adrenal cortex due to increased circulating levels of ACTH (hyperfunction), often via pituitary tumour.
- Excessive production of glucocorticoids as well as mineralocorticoids.
Describe the problems caused by Cushing’s disease related to glucocorticoid production.
- Increased blood glucose (adrenal diabetes)
- Increased insulin secretion (if prolonged, beta cells burn out)
- Decreased protein synthesis
- Increased protein breakdown
- Osteoporosis: loss of protein and Ca2+ from bone
- Can cause masculinization in women due to increase in sex steroids
Describe the problems caused by Cushing’s disease related to mineralicorticoid production.
- Plasma: increased Na+, Cl-, H2O - reabsorbed from urine
- Leads to increased extracellular fluid, plasma volume, hypertension
- Decreased K+ (hypokalemia), H+ (alkalosis) - lost in urine
- Also causes masculinization in women due to increase in sex steroids
What are the diagnostic features of Cushing’s disease?
- Puffiness of face
- Masculinizing effect
- Hypertension
- Increased blood glucose
- Increased steroid metabolites in urine
What is the treatment for Cushing’s disease?
Surgery: subtotal removal of adrenal cortex
What is the treatment for Addison’s disease?
- Cortisol administration to improve carbohydrate metabolism
- Aldosterone administration to control electrolyte blood levels.
Where is the pancreas located?
Behind the stomach
What is the main function of the pancreas?
99% of the pancreas is exocrine and secretes digestive enzymes. However, it also has small endocrine structures called the islets of Langerhans. They have beta cells that produce insulin and alpha cells that produce glucagon.
Describe the cellular composition of the islets of Langerhans and what they produce.
- 60% of cells are beta cells, which synthesize insulin
- 25% of cells are alpha cells, which synthesize glucagon
What is the type and function of insulin and glucagon?
Small protein hormones and both control of glucose concentration in blood
Compare the importance of insulin and glucagon and explain why.
Insulin is more important than glucagon and insulin deficiency or absence compromises the wellbeing of the individual, possibly leading to death.
Glucagon function is somewhat redundant with that of glucocorticoids.
What is the main function of insulin?
It is the only hormone that acts primarily to decrease blood glucose by transporting it into the cell, where there is very little free glucose.
What is the fate of glucose once it is transported into the cell by insulin?
a) in the liver and muscle cells it is converted to glycogen
b) in the adipose tissue it is converted to fat and stored for later use
c) in many cells of the body it is oxidized to produce energy
What is the role of insulin receptors?
Stimulates the insertion of glucose transport proteins stored in the cytoplasm into the plasma membrane, increasing glucose uptake.
What is the cause of insulin deficiency?
Results when beta cells are destroyed, leading to diabetes mellitus. Make tissues cannot take up glucose and glucose accumulates in the circulation.
This will occur even without glucose in the diet because of increased gluconeogenesis.
When insulin deficiency occurs, what is the principal source of energy for cells? How does this affect the composition and pH of the circulation?
Under these conditions, free fatty acids become the principle source of energy -> increased lipolysis.
However, they are inefficiently used, leading to incomplete oxidation of fatty acids and increased circulating acetoacetic acid and beta-hydroxybutyric acid (metabolic acidosis) and acetone. -> smell of acetone in breathe of untreated diabetics.
Leads to decreased blood pH, diabetic coma, and death unless treatment is provided.
Insulin deficiency due to the destruction of beta cells leads to the condition […]
diabetes mellitus
Aside from direct impacts on the circulation, name 3 other symptoms of diabetes mellitus.
- At >180 mg% glucose spills over into the urine, causing glucosurea
- Leads to loss of water in urine, causing polyurea - dehydration and increased thirst (polydipsia). As mentioned above, untreated diabetes leads to ketosis, and metabolic acidosis.
What is the treatment for diabetes mellitus?
- Administration of insulin is needed to restore individual back to normal.
- In diabetic comas, acidosis and associated electrolyte imbalance must be corrected in addition to insulin administration.
What are the two types of diabetes mellitus? Explain the difference between them.
In adults, diabetes mellitus might be due to a deficiency of insulin (type 1) or hyporesponsiveness to insulin (type 2)
How much glucose is typically present in the bloodstream?
Present at around 80 mg/100 ml. However, there is very little free in the tissues.
What is the effect of administering too much insulin in response to type 1 diabetes? Include key metrics.
Too much insulin could lead to severe decrease in blood glucose content. When blood glucose reaches 20-30 mg/100 ml, the availability of glucose for the brain is not sufficient and the individual can fall into insulin shock/hypoglycemic coma. This can kill the individual if they are not administered glucose immediately.
In type 2 diabetes, insulin levels are […]
normal or abnormally high
What is the cause of type 2 diabetes?
The problem is hyporesponsiveness to of target cells to insulin via a decreased number (downregulation) of insulin receptors on target cells. This often associated with obesity due to overeating.
What is the treatment for type 2 diabetes?
Proper diet and exercise. Decreased caloric intake, decreased insulin, upregulation of receptors. Insulin receptors increase in response to frequent endurance exercise, independent to changes in body weight.
What is the cause of juvenile diabetes mellitus? What is the treatment?
Juvenile diabetes appears in childhood and is insulin dependent. The beta cells of the pancreas do not produce insulin. Treatment requires administration of insulin.
How is a glucose tolerance test administered?
After an overnight fast, patient given 0.75 to 1.5 g of glucose/kg body weight. Blood is taken before administration and at 30-60 min intervals for 3-4 hours, and glucose is measured.
How does glucose tolerance differ between normal and diabetic individuals?
Blood glucose in a normal individual increases in 1 hr from 80g/100 ml to 130 mg/100 ml and returns to normal after 2-3 hours.
In a diabetic, increase in blood glucose is greater and returns to normal more slowly.
Name the primary and secondary controls of insulin secretion and how they work.
Most important: beta cells respond to levels of blood glucose, secreting little or no insulin when blood glucose is low, secreting much more when the blood glucose is high.
Also, release of gastrin and vagal impulses to the beta cells induce insulin release, as a result insulin starts to leave the pancreas even before the blood glucose begins to rise during meals.
