A 33-year-old woman presents to her physician's office for a postpartum check-up. She gave birth to a full-term boy via an uncomplicated vaginal delivery 3 weeks ago and has been exclusively breastfeeding her son. The hormone most responsible for promoting milk let-down during lactation in this new mother would lead to the greatest change in the level of which of the following factors?
Q2
A 68-year-old man is brought to the emergency department 30 minutes after collapsing on the street. On arrival, he is obtunded. His pulse is 110/min and blood pressure is 250/120 mm Hg. A CT scan of the head shows an intracerebral hemorrhage involving bilateral thalamic nuclei and the third ventricle. Cortical detection of which of the following types of stimuli is most likely to remain unaffected in this patient?
Q3
A medical student volunteers for an experiment in the physiology laboratory. Before starting the experiment, her oral temperature is recorded as 36.9°C (98.4°F). She is then made to dip both her hands in a bowl containing ice cold water. She withdraws her hands out of the water, and finds that they look pale and feel very cold. Her oral temperature is recorded once more and is found to be 36.9°C (98.4°F) even though her hands are found to be 4.5°C (40.0°F). Which of the following mechanisms is responsible for the maintenance of her temperature throughout the experiment?
Q4
A previously healthy 35-year-old woman comes to the physician because of palpitations and anxiety for the past 2 months. She has had a 3.1-kg (7-lb) weight loss in this period. Her pulse is 112/min. Cardiac examination shows normal heart sounds with a regular rhythm. Neurologic examination shows a fine resting tremor of the hands; patellar reflexes are 3+ bilaterally with a shortened relaxation phase. Urine pregnancy test is negative. Which of the following sets of laboratory values is most likely on evaluation of blood obtained before treatment?
| TSH | Free T4 | Free T3 | Thyroxine-binding globulin |
Q5
A 50-year-old man presents to the emergency department due to altered mental status. His symptoms began approximately two weeks prior to presentation where he complained of increasing fatigue, malaise, loss of appetite, and subjective fever. Vital signs are significant for a temperature of 102.0°F (38.9°C). On physical examination, there is a holosystolic murmur in the tricuspid area, linear non-blanching reddish lesions under the nails, and needle tracks on both antecubital fossa. A transthoracic echocardiogram shows a vegetation on the tricuspid valve. Blood cultures return positive for Staphylococcus aureus. A lumbar puncture is prompted due to altered mental status in the setting of fever; however, there is no bacteria found on cerebral spinal fluid (CSF) culture. Which of the following cell structures prevents the penetration of the bacteria into the CSF from his blood?
Q6
A 32-year-old woman presents to the clinic with complaints of insomnia, diarrhea, anxiety, thinning hair, and diffuse muscle weakness. She has a family history of type 1 diabetes mellitus and thyroid cancer. She drinks 1–2 glasses of wine weekly. Her vital signs are unremarkable. On examination, you notice that she also has bilateral exophthalmos. Which of the following results would you expect to see on a thyroid panel?
Q7
A 60-year-old obese man comes to the emergency department with tightness in his chest and lower extremity edema. He has a history of heart failure that has gotten worse over the last several years. He takes finasteride, lisinopril, and albuterol. He does not use oxygen at home. He has mildly elevated blood pressure, and he is tachycardic and tachypneic. Physical examination shows an overweight man having difficulty speaking with 2+ pitting edema on his lower extremities up to his thighs. The attending asks you to chart out the patient's theoretical cardiac function curve from where it was 5 years ago when he was healthy to where it is right now. What changes occurred in the last several years without compensation?
Q8
You have been asked to deliver a lecture to medical students about the effects of various body hormones and neurotransmitters on the metabolism of glucose. Which of the following statements best describes the effects of sympathetic stimulation on glucose metabolism?
Q9
A 12-year-old girl is brought to the emergency department 3 hours after the sudden onset of colicky abdominal pain and vomiting. She also has redness and swelling of the face and lips without pruritus. Her symptoms began following a tooth extraction earlier this morning. She had a similar episode of facial swelling after a bicycle accident 1 year ago which resolved within 48 hours without treatment. Vital signs are within normal limits. Examination shows a nontender facial edema, erythema of the oral mucosa, and an enlarged tongue. The abdomen is soft and there is tenderness to palpation over the lower quadrants. An abdominal ultrasound shows segmental thickening of the intestinal wall. Which of the following is the most likely cause of this patient's condition?
Q10
A 49-year-old male complains of heartburn, epigastric pain, and diarrhea. He has a past medical history significant for heartburn that is nonresponsive to omeprazole. He denies any alcohol intake, and has not been taking any nonsteroidal anti-inflammatory drugs. An endoscopy is performed, which shows two ulcers in the proximal duodenum, and one in the distal third of the duodenum. Which of the following is most likely true about this patient’s current condition?
Cardiovascular US Medical PG Practice Questions and MCQs
Question 1: A 33-year-old woman presents to her physician's office for a postpartum check-up. She gave birth to a full-term boy via an uncomplicated vaginal delivery 3 weeks ago and has been exclusively breastfeeding her son. The hormone most responsible for promoting milk let-down during lactation in this new mother would lead to the greatest change in the level of which of the following factors?
A. Ras
B. Phospholipase A
C. cGMP
D. cAMP
E. IP3 (Correct Answer)
Explanation: ***IP3***
- The hormone responsible for milk let-down is **oxytocin**, which acts via **Gq protein-coupled receptors**.
- Gq protein activation leads to the activation of **phospholipase C**, which hydrolyzes **PIP2** into **IP3** (inositol triphosphate) and DAG (diacylglycerol). IP3 then signals the release of intracellular calcium.
*Ras*
- **Ras** is a small GTPase involved in signal transduction pathways, typically associated with **receptor tyrosine kinases** and cell growth/differentiation, not primarily with oxytocin signaling for milk let-down.
- It plays a role in the **MAP kinase pathway**, distinct from the Gq protein pathway activated by oxytocin.
*Phospholipase A*
- **Phospholipase A** enzymes (PLA1, PLA2, PLC, PLD) hydrolyze phospholipids, but **phospholipase A2** is primarily known for producing **arachidonic acid**, a precursor to prostaglandins and leukotrienes, which is not the main downstream effector of oxytocin.
- While phospholipases are involved in lipid signaling, **phospholipase C** is the specific enzyme activated by oxytocin's Gq pathway leading to IP3 production.
*cGMP*
- **cGMP** (cyclic guanosine monophosphate) is a second messenger typically produced by **guanylyl cyclases** in response to nitric oxide or natriuretic peptides.
- It is involved in processes like **vasodilation** and smooth muscle relaxation, distinct from the oxytocin pathway for milk ejection.
*cAMP*
- **cAMP** (cyclic adenosine monophosphate) is a common second messenger generated by **adenylyl cyclase** following activation of **Gs protein-coupled receptors**.
- While important in many hormonal pathways, it is not the primary signaling molecule downstream of oxytocin's action on its receptors for milk let-down, which predominantly uses the Gq pathway.
Question 2: A 68-year-old man is brought to the emergency department 30 minutes after collapsing on the street. On arrival, he is obtunded. His pulse is 110/min and blood pressure is 250/120 mm Hg. A CT scan of the head shows an intracerebral hemorrhage involving bilateral thalamic nuclei and the third ventricle. Cortical detection of which of the following types of stimuli is most likely to remain unaffected in this patient?
A. Visual
B. Gustatory
C. Facial fine touch
D. Proprioception
E. Olfactory (Correct Answer)
Explanation: ***Olfactory***
- The **olfactory pathway** is unique among sensory modalities as it is the only one that **bypasses the thalamus** and projects directly to the **olfactory cortex** (piriform cortex), which is not affected by the thalamic hemorrhage.
- While the patient is obtunded, cortical detection of olfactory stimuli itself could theoretically remain intact if the relevant cortical areas are preserved.
*Visual*
- **Visual pathways** rely heavily on the **lateral geniculate nucleus (LGN)** of the thalamus for relaying information from the retina to the visual cortex.
- Damage to the thalamus, especially in a hemorrhage affecting bilateral nuclei, would severely compromise visual processing.
*Gustatory*
- **Gustatory (taste) pathways** involve a relay in the **ventral posteromedial nucleus (VPM)** of the thalamus before projecting to the gustatory cortex.
- A thalamic hemorrhage would therefore impair the transmission of taste information to the cortex.
*Facial fine touch*
- **Fine touch sensation from the face** is relayed through the **ventral posteromedial nucleus (VPM)** of the thalamus, which processes sensory input from the trigeminal system.
- Bilateral thalamic hemorrhage would disrupt this somatosensory pathway, affecting detectable fine touch.
*Proprioception*
- **Proprioception**, the sense of body position and movement, is relayed primarily through the **ventral posterolateral nucleus (VPL)** of the thalamus.
- Damage to the thalamus would significantly impair the transmission of proprioceptive information to the somatosensory cortex.
Question 3: A medical student volunteers for an experiment in the physiology laboratory. Before starting the experiment, her oral temperature is recorded as 36.9°C (98.4°F). She is then made to dip both her hands in a bowl containing ice cold water. She withdraws her hands out of the water, and finds that they look pale and feel very cold. Her oral temperature is recorded once more and is found to be 36.9°C (98.4°F) even though her hands are found to be 4.5°C (40.0°F). Which of the following mechanisms is responsible for the maintenance of her temperature throughout the experiment?
A. Shivering
B. Muscular contraction
C. Cutaneous vasoconstriction (Correct Answer)
D. Diving reflex
E. Endogenous pyrogen release
Explanation: **Cutaneous vasoconstriction**
- **Cutaneous vasoconstriction** reduces blood flow to the skin, minimizing heat loss from the core to the periphery and maintaining **core body temperature**.
- The pale and cold hands indicate significant vasoconstriction, diverting blood away from the extremities to protect the more vital internal organs.
*Shivering*
- **Shivering** is a mechanism for generating heat through rapid, involuntary muscle contractions.
- While it increases heat production, it would only be activated if the **core body temperature** began to drop, which did not happen in this scenario.
*Muscular contraction*
- **Muscular contraction** can generate heat, but it is typically a more generalized response to cold or a component of shivering.
- In this localized cold exposure, other mechanisms are primarily responsible for maintaining the overall **core temperature**.
*Diving reflex*
- The **diving reflex** involves bradycardia, peripheral vasoconstriction, and blood redistribution to protect the brain and heart during submersion.
- While it includes vasoconstriction, its primary trigger is face immersion in cold water (or apnea), and its systemic effects are more pronounced than what's described in this localized hand immersion.
*Endogenous pyrogen release*
- **Endogenous pyrogen release** leads to fever by resetting the hypothalamic thermoregulatory set point to a higher level.
- This mechanism is associated with infection or inflammation and would cause a systemic increase in body temperature, not the maintenance of a normal temperature in response to localized cold.
Question 4: A previously healthy 35-year-old woman comes to the physician because of palpitations and anxiety for the past 2 months. She has had a 3.1-kg (7-lb) weight loss in this period. Her pulse is 112/min. Cardiac examination shows normal heart sounds with a regular rhythm. Neurologic examination shows a fine resting tremor of the hands; patellar reflexes are 3+ bilaterally with a shortened relaxation phase. Urine pregnancy test is negative. Which of the following sets of laboratory values is most likely on evaluation of blood obtained before treatment?
| TSH | Free T4 | Free T3 | Thyroxine-binding globulin |
A. ↓ ↑ ↑ normal (Correct Answer)
B. ↑ ↓ ↓ ↓
C. ↓ ↓ ↓ normal
D. ↑ normal normal normal
E. ↓ ↑ normal ↑
Explanation: ***↓ ↑ ↑ normal***
- The patient presents with classic symptoms of **hyperthyroidism**, including palpitations, anxiety, weight loss, tachycardia, and a fine resting tremor. These symptoms are consistent with an **elevated metabolic state** caused by excess thyroid hormones.
- In primary hyperthyroidism, the thyroid gland overproduces T4 and T3, leading to **high levels of free T3 and free T4**. This increased feedback inhibits the pituitary, causing a **decreased TSH** level. Thyroxine-binding globulin (TBG) levels are typically normal in uncomplicated hyperthyroidism.
*↑ ↓ ↓ ↓*
- This pattern of laboratory values (high TSH, low free T4, low free T3) is characteristic of **primary hypothyroidism**, where the thyroid gland is underactive and fails to produce sufficient thyroid hormones. This directly contradicts the patient's hyperthyroid symptoms.
- A low TBG level can occur in conditions like severe liver disease or nephrotic syndrome, but it does not align with the patient's clinical presentation of hyperthyroidism.
*↓ ↓ ↓ normal*
- While a low TSH is consistent with hyperthyroidism, low free T4 and free T3 levels signify **hypothyroidism**. This combination would suggest **secondary or central hypothyroidism**, where the pituitary gland is not stimulating the thyroid sufficiently.
- This scenario would present with symptoms of hypometabolism (e.g., fatigue, weight gain, bradycardia), which are antithetical to the patient's symptoms.
*↑ normal normal normal*
- A high TSH with normal free T4 and free T3 levels suggests **subclinical hypothyroidism**, where the thyroid gland is beginning to fail, but peripheral hormone levels are still within the normal range.
- This pattern does not explain the pronounced hyperthyroid symptoms experienced by the patient, which point to significantly elevated thyroid hormone levels.
*↓ ↑ normal ↑*
- This option presents a low TSH and high free T4, which is consistent with hyperthyroidism. However, a **normal free T3** would be unusual in overt hyperthyroidism, as both T3 and T4 are typically elevated.
- An elevated **TBG** is often seen in conditions like pregnancy or estrogen therapy, which would increase total T4 but usually result in normal free T4. This pattern does not fully align with the patient's clinical picture of active hyperthyroidism.
Question 5: A 50-year-old man presents to the emergency department due to altered mental status. His symptoms began approximately two weeks prior to presentation where he complained of increasing fatigue, malaise, loss of appetite, and subjective fever. Vital signs are significant for a temperature of 102.0°F (38.9°C). On physical examination, there is a holosystolic murmur in the tricuspid area, linear non-blanching reddish lesions under the nails, and needle tracks on both antecubital fossa. A transthoracic echocardiogram shows a vegetation on the tricuspid valve. Blood cultures return positive for Staphylococcus aureus. A lumbar puncture is prompted due to altered mental status in the setting of fever; however, there is no bacteria found on cerebral spinal fluid (CSF) culture. Which of the following cell structures prevents the penetration of the bacteria into the CSF from his blood?
A. Hemidesmosomes
B. Capillary fenestrations
C. Tight junctions (Correct Answer)
D. Desmosomes
E. Gap junctions
Explanation: ***Tight junctions***
- **Tight junctions** between endothelial cells of brain capillaries form the **blood-brain barrier**, restricting the passage of bacteria and other large molecules from the bloodstream into the cerebrospinal fluid.
- While bacteria are present systemically (causing endocarditis), the integrity of these tight junctions prevents their entry into the central nervous system, explaining the **negative CSF culture**.
*Hemidesmosomes*
- **Hemidesmosomes** are cell junctions that anchor cells to the **basement membrane**, providing structural integrity to epithelial tissues.
- They are not involved in controlling the permeability of the **blood-brain barrier** or preventing bacterial penetration into the CSF.
*Capillary fenestrations*
- **Capillary fenestrations** are pores in the endothelial cells of certain capillaries (e.g., kidneys, endocrine glands) that allow for rapid exchange of substances.
- Brain capillaries, unlike these, are characterized by a **lack of fenestrations** as a key component of the blood-brain barrier, specifically to restrict molecular passage.
*Desmosomes*
- **Desmosomes** provide strong cell-to-cell adhesion by anchoring to intermediate filaments, commonly found in tissues subject to mechanical stress (e.g., skin, heart muscle).
- They do not form a permeability barrier and are not a feature of the **blood-brain barrier** that prevents bacterial invasion.
*Gap junctions*
- **Gap junctions** are channels that allow direct passage of ions and small molecules between adjacent cells, facilitating intercellular communication.
- They are not involved in regulating the passage of large entities like bacteria across a cellular barrier such as the **blood-brain barrier**.
Question 6: A 32-year-old woman presents to the clinic with complaints of insomnia, diarrhea, anxiety, thinning hair, and diffuse muscle weakness. She has a family history of type 1 diabetes mellitus and thyroid cancer. She drinks 1–2 glasses of wine weekly. Her vital signs are unremarkable. On examination, you notice that she also has bilateral exophthalmos. Which of the following results would you expect to see on a thyroid panel?
A. Low TSH, low T4, low T3
B. High TSH, high T4, high T3
C. Low TSH, high T4, high T3 (Correct Answer)
D. High TSH, low T4, low T3
E. Normal TSH, high T4, high T3
Explanation: ***Low TSH, high T4, high T3***
- The patient's symptoms (insomnia, diarrhea, anxiety, thinning hair, muscle weakness, and exophthalmos) are classic for **hyperthyroidism**, specifically **Graves' disease**.
- In primary hyperthyroidism, the thyroid gland overproduces T4 and T3, leading to high levels of these hormones and a compensatory **suppression of TSH** due to negative feedback.
*Low TSH, low T4, low T3*
- This pattern is indicative of **central or secondary hypothyroidism**, where a problem with the pituitary gland prevents adequate TSH production, subsequently leading to low T4 and T3.
- The patient's symptoms of hyperthyroidism (e.g., exophthalmos, anxiety, diarrhea) contradict this hormonal profile.
*High TSH, high T4, high T3*
- This combination is rare and suggests **TSH-secreting pituitary adenoma** (secondary hyperthyroidism) or resistance to thyroid hormone.
- While it involves elevated thyroid hormones, the elevated TSH is a key differentiator from primary hyperthyroidism like Graves' disease.
*High TSH, low T4, low T3*
- This is the hallmark of **primary hypothyroidism**, where the thyroid gland is underactive and cannot produce enough T4 and T3, causing the pituitary to release more TSH in an attempt to stimulate it.
- The patient's symptoms (e.g., insomnia, anxiety, diarrhea, exophthalmos) are directly opposite to those seen in hypothyroidism.
*Normal TSH, high T4, high T3*
- While it involves elevated thyroid hormones, a **normal TSH** with high T4/T3 is highly atypical for hyperthyroidism and would prompt suspicion of laboratory error or assay interference.
- In true hyperthyroidism, TSH would virtually always be suppressed due to the negative feedback mechanism.
Question 7: A 60-year-old obese man comes to the emergency department with tightness in his chest and lower extremity edema. He has a history of heart failure that has gotten worse over the last several years. He takes finasteride, lisinopril, and albuterol. He does not use oxygen at home. He has mildly elevated blood pressure, and he is tachycardic and tachypneic. Physical examination shows an overweight man having difficulty speaking with 2+ pitting edema on his lower extremities up to his thighs. The attending asks you to chart out the patient's theoretical cardiac function curve from where it was 5 years ago when he was healthy to where it is right now. What changes occurred in the last several years without compensation?
A. Cardiac output went up, and right atrial pressure went down
B. Cardiac output went down, and right atrial pressure went down
C. Cardiac output went up, and right atrial pressure went up
D. Cardiac output went down, and right atrial pressure went up (Correct Answer)
E. Both cardiac output and right atrial pressures are unchanged
Explanation: ***Cardiac output went down, and right atrial pressure went up***
- In **uncompensated heart failure**, the heart's pumping efficiency decreases, leading to a **reduced cardiac output** as the cardiac function curve shifts downward.
- The inability to pump blood forward effectively causes blood to back up in the venous system, increasing **venous pressure** and, consequently, **right atrial pressure**, shifting the curve to the right.
- This represents the **Frank-Starling relationship without compensatory mechanisms** such as sympathetic activation, fluid retention, or cardiac remodeling.
*Cardiac output went up, and right atrial pressure went down*
- An **increased cardiac output** with a **decreased right atrial pressure** would suggest improved cardiac function, which is contrary to the patient's worsening heart failure symptoms.
- This scenario would typically be seen in states of increased demand with good cardiac reserve, not decompensated heart failure.
*Cardiac output went down, and right atrial pressure went down*
- While **cardiac output decreases** in heart failure, **right atrial pressure typically increases** due to backward pressure from circulatory congestion.
- A decrease in both would be unusual in this context and might suggest conditions like **hypovolemia**, which is not indicated by the patient's significant edema.
*Cardiac output went up, and right atrial pressure went up*
- An **increased cardiac output** is inconsistent with the progression of **heart failure**, which is characterized by a decline in the heart's ability to pump.
- While right atrial pressure would be elevated, the upward trend in cardiac output would indicate a different physiological state, perhaps a high-output heart failure, but the overall clinical picture suggests a low-output state.
*Both cardiac output and right atrial pressures are unchanged*
- The patient's presentation with worsening chest tightness and lower extremity edema clearly indicates a **deterioration in cardiac function**, meaning changes in cardiac output and right atrial pressure must have occurred.
- Unchanged parameters would imply a stable condition, which is not the case for this patient with progressive heart failure.
Question 8: You have been asked to deliver a lecture to medical students about the effects of various body hormones and neurotransmitters on the metabolism of glucose. Which of the following statements best describes the effects of sympathetic stimulation on glucose metabolism?
A. Norepinephrine causes increased glucose absorption within the intestines.
B. Without epinephrine, insulin cannot act on the liver.
C. Peripheral tissues require epinephrine to take up glucose.
D. Epinephrine increases liver glycogenolysis. (Correct Answer)
E. Sympathetic stimulation to alpha receptors of the pancreas increases insulin release.
Explanation: ***Epinephrine increases liver glycogenolysis.***
- **Epinephrine**, released during sympathetic stimulation, primarily acts to increase **glucose availability** for immediate energy.
- It achieves this by stimulating **glycogenolysis** (breakdown of glycogen into glucose) in the liver via **beta-adrenergic receptors**.
*Norepinephrine causes increased glucose absorption within the intestines.*
- **Norepinephrine** primarily causes **vasoconstriction** and can *decrease* **intestinal motility** and nutrient absorption due to shunting blood away from the digestive tract during stress.
- Glucose absorption is mainly regulated by digestive enzymes and transport proteins, not directly increased by norepinephrine.
*Without epinephrine, insulin cannot act on the liver.*
- **Insulin** acts on the liver independent of epinephrine to promote **glucose uptake**, **glycogenesis**, and **lipid synthesis**.
- Epinephrine and insulin have **antagonistic effects** on liver glucose metabolism; epinephrine increases glucose output, while insulin decreases it.
*Peripheral tissues require epinephrine to take up glucose.*
- **Insulin** is the primary hormone required for **glucose uptake** by most peripheral tissues, especially **muscle** and **adipose tissue**, via **GLUT4 transporters**.
- Epinephrine generally *reduces* glucose uptake by peripheral tissues to preserve glucose for the brain during stress.
*Sympathetic stimulation to alpha receptors of the pancreas increases insulin release.*
- Sympathetic stimulation, primarily acting through **alpha-2 adrenergic receptors** on pancreatic beta cells, actually **inhibits** **insulin secretion**.
- This inhibition helps to increase blood glucose levels by reducing insulin's glucose-lowering effects.
Question 9: A 12-year-old girl is brought to the emergency department 3 hours after the sudden onset of colicky abdominal pain and vomiting. She also has redness and swelling of the face and lips without pruritus. Her symptoms began following a tooth extraction earlier this morning. She had a similar episode of facial swelling after a bicycle accident 1 year ago which resolved within 48 hours without treatment. Vital signs are within normal limits. Examination shows a nontender facial edema, erythema of the oral mucosa, and an enlarged tongue. The abdomen is soft and there is tenderness to palpation over the lower quadrants. An abdominal ultrasound shows segmental thickening of the intestinal wall. Which of the following is the most likely cause of this patient's condition?
A. T-cell mediated immune reaction
B. Drug-induced bradykinin excess
C. Leukotriene overproduction
D. Immune-complex deposition
E. Complement inhibitor deficiency (Correct Answer)
Explanation: ***Complement inhibitor deficiency***
- This patient's presentation with recurrent episodes of **angioedema** (face and lip swelling, enlarged tongue, intestinal wall thickening causing abdominal pain), particularly triggered by **trauma** (tooth extraction, bicycle accident), strongly suggests **hereditary angioedema (HAE)**. HAE is caused by a deficiency or dysfunction of **C1 esterase inhibitor**, a key complement inhibitor.
- A deficiency in C1 esterase inhibitor leads to uncontrolled activation of both the **complement cascade** and the **kallikrein-bradykinin pathway**, resulting in excessive **bradykinin production**, which causes increased vascular permeability and localized edema without urticaria or pruritus.
*T-cell mediated immune reaction*
- **T-cell mediated reactions** are typically associated with **delayed-type hypersensitivity reactions** (e.g., contact dermatitis, graft rejection) and **autoimmune disorders**, which do not fit the acute, recurrent, non-pruritic angioedema seen here.
- These reactions primarily involve cell-mediated cytotoxicity or cytokine release, rather than rapid fluid extravasation due to bradykinin excess.
*Drug-induced bradykinin excess*
- While drug-induced angioedema (e.g., from **ACE inhibitors**) can also cause bradykinin excess, this patient's history of episodes since childhood (after a bicycle accident) and the current exacerbation after a tooth extraction, makes a **hereditary predisposition** much more likely than an isolated drug reaction in a 12-year-old.
- The triggers (trauma, dental procedure) are classic for HAE, which involves an intrinsic defect in bradykinin regulation, not merely an external pharmaceutical cause.
*Leukotriene overproduction*
- **Leukotrienes** are potent mediators involved in **allergic reactions** and **asthma**, contributing to bronchoconstriction, vascular permeability, and inflammation.
- Conditions involving leukotriene overproduction, such as aspirin-exacerbated respiratory disease, typically present with bronchospasm, rhinitis, or urticaria, which are not the primary features here.
*Immune-complex deposition*
- **Immune-complex deposition** is characteristic of conditions like **serum sickness**, **lupus nephritis**, or **vasculitis**, leading to inflammation, fever, rash, and organ damage.
- These conditions do not typically present with isolated, recurrent, non-pruritic angioedema and do not involve the specific mechanism of bradykinin overproduction seen in this patient.
Question 10: A 49-year-old male complains of heartburn, epigastric pain, and diarrhea. He has a past medical history significant for heartburn that is nonresponsive to omeprazole. He denies any alcohol intake, and has not been taking any nonsteroidal anti-inflammatory drugs. An endoscopy is performed, which shows two ulcers in the proximal duodenum, and one in the distal third of the duodenum. Which of the following is most likely true about this patient’s current condition?
A. Chronic atrophic gastritis would decrease the suspected hormone level
B. Secretin administration would suppress the release of the suspected hormone in this patient
C. Parietal cell hypertrophy is likely present (Correct Answer)
D. The suspected hormone acts via a receptor tyrosine kinase signaling pathway
E. Increasing omeprazole dose will likely decrease the suspected hormone level
Explanation: ***Parietal cell hypertrophy is likely present***
- The patient's symptoms (refractory heartburn, epigastric pain, diarrhea, and multiple duodenal ulcers, including distal ones) are highly suggestive of **Zollinger-Ellison syndrome (ZES)**, caused by a gastrinoma.
- **Gastrinomas** overproduce gastrin, which leads to **parietal cell hyperplasia and hypertrophy** due to its trophic effects and excessive acid secretion. This results in the observed multiple, refractory ulcers.
*Chronic atrophic gastritis would decrease the suspected hormone level*
- **Chronic atrophic gastritis** typically causes a *decrease* in gastric acid production due to glandular atrophy and loss of parietal cells.
- This reduction in acid secretion would lead to an *increase* in gastrin release as a feedback mechanism, trying to stimulate acid production, not a decrease.
*Secretin administration would suppress the release of the suspected hormone in this patient*
- In healthy individuals, **secretin** *inhibits* gastrin release from G cells, but in patients with **gastrinomas**, secretin paradoxically *stimulates* gastrin release.
- A positive secretin stimulation test (rise in gastrin levels after secretin administration) is a diagnostic hallmark for gastrinoma.
*The suspected hormone acts via a receptor tyrosine kinase signaling pathway*
- The suspected hormone, **gastrin**, exerts its effects primarily by binding to the **cholecystokinin B (CCK2) receptor**, which is a **G protein-coupled receptor (GPCR)**.
- Activation of this GPCR leads to increased intracellular calcium and protein kinase C activity, not a receptor tyrosine kinase pathway.
*Increasing omeprazole dose will likely decrease the suspected hormone level*
- While omeprazole *reduces acid secretion* and may alleviate symptoms, it does so by inhibiting the proton pump in parietal cells.
- Reducing acid output through omeprazole would *increase* gastrin release via a feedback loop, as the body tries to compensate for the perceived lack of acid, rather than decreasing gastrin levels in ZES patients.
