Frank is a 52-year-old male who began to feel unwell 4 months ...

[Kthamas]

Frank is a 52-year-old male who began to feel unwell 4 months ago. His appetite declined, and he could not taste food as well as he used to. When he lost a considerable amount of weight and became weak as a result, he visited his doctor.
 
  The examination revealed Frank had adenocarcinoma of the pancreas, and surgery was immediately ordered. During his hospitalization, Fred was slow to gain weight and his muscles were wasted. In order to build up his strength for chemotherapy, his wife tried to tempt him with freshly baked cookies and sweets she brought from home.
 
  In severe protein-calorie malnutrition, what is a potential complication of rapid enteral refeeding? What effects does protein-calorie malnutrition have on the gastrointestinal system?
 
  What might Frank's nitrogen balance be? Why would he have this type of nitrogen balance?
 
  Frank's nurses encourage him to eat the potatoes and dinner rolls that come with his meals. Why are they encouraging Frank to complete the carbohydrates on his plate?

Question 2

Leda is a 38-year-old woman who began to experience weight gain, mood swings, and weakness. When her periods became irregular, she went to her physician.
 
  Leda's physician heard the symptoms Leda was concerned about and then ordered a 24-hour free cortisol urine test and an overnight dexamethasone suppression test and measured her serum ACTH levels. The results indicated that Leda had Cushing disease, a condition caused by the hypersecretion of ACTH by the anterior pituitary and resulting in elevated cortisol levels. To confirm the diagnosis, Leda's physician ordered a cranial MRI to identify the presence of a pituitary tumor.
 
  The dexamethasone test involves the administration of a synthetic glucocorticoid (i.e., cortisol). Knowing what you do about negative feedback mechanisms, how might this test be used to assess pituitary function?
 
  Describe how the steroid hormones, like cortisol, are metabolized in the body. What are the advantages of using a 24-hour urine test to measure this hormone?
 
  Protein-based and steroid-based hormones trigger cellular responses in different ways. What are the differences between the mechanism of action of ACTH and cortisol on target cells?

[cupcake16]

Answer to Question 1

Enteral feeding, particularly in the very malnourished individual, can result in symptoms associated with malabsorption. In protein-calorie malnutrition, there is atrophy of the gastrointestinal mucosal layer. Intestinal villi are also lost. Enteral refeeding can therefore produce malabsorptive symptoms if the intestinal mucosa is unable to process ingested nutrients.

Frank is likely to be in negative nitrogen balance. Protein is the only source of nitrogen for the body. When protein intake matches nitrogen excretion, an individual is in nitrogen balance. In situations where there is tissue breakdown from illness or decrease in dietary protein, nitrogen loss exceeds intake. Frank's pancreatic cancer and loss of appetite would result in tissue catabolism, creating a state of negative nitrogen balance.

Carbohydrates in the diet ensure energy requirements are met without converting proteins or fats to usable energy sources. Ketone production has the effect of decreasing appetite, an undesirable effect in those who are ill or underweight. Protein and fat metabolism also generates metabolic wastes that are osmotically active. Renal excretion of these wastes can lead to dehydration and electrolyte imbalances. A diet containing carbohydrates is therefore necessary to prevent the catabolism of tissue proteins and the production of ketone bodies.

Answer to Question 2

Suppression tests are particularly valuable when determining the hyperfunction of an endocrine gland. In an intact negative feedback mechanism, the administration of a hormone would suppress the action of the endocrine gland regulating its release. Therefore, in a healthy individual, the administration of a glucocorticoid would suppress the activity of the hypothalamic-pituitary complex. If suppression does not occur, the pituitary may be in a state of hyperfunction and unresponsive to serum cortisol levels.

Cortisol and other steroid hormones are inactivated when bound to protein carriers. The hormones are conjugated in the liver and then excreted in the bile and urine. By measuring hormone levels in the urine, hormone status is more accurately determined from a 24-hour sample instead of an isolated sample from one moment in the day. Urine is also easy to collect and less invasive than blood sampling.

Protein-based hormones exert their effects by binding to surface receptors on cell membranes. The binding of the hormone may act to stimulate the activity of second messengers (i.e., cAMP). Alternatively, the binding may initiate a direct response by the cell by causing ion (i.e., calcium) channels to open. Steroid hormones are fat soluble and therefore pass directly through the cell membrane. Once inside the cell, they bind to intracellular receptors. These hormone-messenger complexes move to the nucleus and act to stimulate or suppress the gene activity of the cell. Whether by surface or intracellular receptors, hormones act to alter the protein synthesis and therefore function of the cell.

[Kthamas]

Gracias!

[ktidd]

Excellent