MDS PREP
What is the typical age of onset for children with growth hormone deficiency due to hypopituitarism?
1) At birth
2) During infancy
3) At the onset of puberty
4) Variable, but often in childhood
Growth hormone deficiency due to hypopituitarism can manifest at different ages depending on the underlying cause. It is often recognized in childhood when growth patterns are monitored regularly.
In hyperparathyroidism, which of the following is a distinctive bone manifestation?
1) Osteomalacia
2) Osteopetrosis
3) Osteitis fibrosa cystica
4) Paget's disease
Osteitis fibrosa cystica is a characteristic bone change seen in hyperparathyroidism. It results from excessive osteoclastic activity and is characterized by the replacement of normal bone marrow with fibrous tissue and cyst-like spaces.
What is the principal cause of megaloblastic anemia other than vitamin B12 deficiency?
1) Folate deficiency
2) Iron deficiency
3) Vitamin A deficiency
4) Vitamin C deficiency
Megaloblastic anemia can be caused by either folate or vitamin B12 deficiency. Both of these nutrients are essential for DNA synthesis and cell division in the bone marrow.
What is the primary hormone responsible for the regulation of phosphate homeostasis?
1) Parathyroid hormone (PTH)
2) Vitamin D
3) Calcitriol
4) Phosphatonin
Parathyroid hormone (PTH) is the primary hormone involved in the regulation of phosphate homeostasis. It acts to increase serum calcium levels and decrease serum phosphate levels by promoting calcium reabsorption and phosphate excretion in the kidneys and stimulating the release of calcium from bones.
In the synthesis of which protein is vitamin K an essential cofactor?
1) Factor II
2) Factor V
3) Factor VIII
4) Factor X
Vitamin K is a crucial cofactor in the carboxylation of glutamate residues in the synthesis of prothrombin (factor II), which is essential for its activity. Vitamin K deficiency can lead to decreased levels of factor II, resulting in a bleeding tendency known as hypoprothrombinemia.
What is the mechanism of action of Clostridium difficile toxins in pseudomembranous colitis?
1) Direct damage to the intestinal mucosal cells
2) Formation of pseudomembranes
3) Inhibition of intestinal peristalsis
4) Alteration of intestinal microbiota composition
The toxins produced by Clostridium difficile cause ribosylation of small GTPases like Rho, leading to disruption of the actin cytoskeleton, increased cytokine release, and epithelial cell apoptosis, which in turn results in the formation of pseudomembranes and the symptoms of pseudomembranous colitis.
What is the primary target of the immune response in Celiac disease?
1) Glia cells in the intestinal mucosa
2) Gluten proteins
3) Enterocytes in the intestinal villi
4) Pancreatic cells
Celiac disease is an autoimmune response to gluten proteins found in wheat, barley, rye, and possibly other grains, which leads to inflammation and damage in the small intestine.
In which layer of the intestinal wall does the mucosal damage occur in Crohn's disease?
1) Mucosa
2) Submucosa
3) Muscularis propria
4) Serosa
Crohn's disease primarily affects the mucosa and submucosa, but can involve all layers of the intestinal wall, leading to the characteristic features such as aphthous ulcers and granulomas.