Endocrine system (thyroid, adrenal, pancreas) US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Endocrine system (thyroid, adrenal, pancreas). These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Endocrine system (thyroid, adrenal, pancreas) US Medical PG Question 1: A scientist in Chicago is studying a new blood test to detect Ab to EBV with increased sensitivity and specificity. So far, her best attempt at creating such an exam reached 82% sensitivity and 88% specificity. She is hoping to increase these numbers by at least 2 percent for each value. After several years of work, she believes that she has actually managed to reach a sensitivity and specificity much greater than what she had originally hoped for. She travels to China to begin testing her newest blood test. She finds 2,000 patients who are willing to participate in her study. Of the 2,000 patients, 1,200 of them are known to be infected with EBV. The scientist tests these 1,200 patients' blood and finds that only 120 of them tested negative with her new exam. Of the patients who are known to be EBV-free, only 20 of them tested positive. Given these results, which of the following correlates with the exam's specificity?
- A. 82%
- B. 90%
- C. 84%
- D. 86%
- E. 98% (Correct Answer)
Endocrine system (thyroid, adrenal, pancreas) Explanation: ***98%***
- **Specificity** measures the proportion of **true negatives** among all actual negatives.
- In this case, 800 patients are known to be EBV-free (actual negatives), and 20 of them tested positive (false positives). This means 800 - 20 = 780 tested negative (true negatives). Specificity = (780 / 800) * 100% = **98%**.
*82%*
- This value represents the *original sensitivity* before the scientist’s new attempts to improve the test.
- It does not reflect the *newly calculated specificity* based on the provided data.
*90%*
- This value represents the *newly calculated sensitivity* of the test, not the specificity.
- Out of 1200 EBV-infected patients, 120 tested negative (false negatives), meaning 1080 tested positive (true positives). Sensitivity = (1080 / 1200) * 100% = 90%.
*84%*
- This percentage is not directly derived from the information given for either sensitivity or specificity after the new test results.
- It does not correspond to any of the calculated values for the new test's performance.
*86%*
- This percentage is not directly derived from the information given for either sensitivity or specificity after the new test results.
- It does not correspond to any of the calculated values for the new test's performance.
Endocrine system (thyroid, adrenal, pancreas) US Medical PG Question 2: A 42-year-old man who is employed as a construction worker presents to his primary care physician with complaints of moderate headaches and profuse sweating. He reports the need to carry up to 3 additional shirt changes to work because they drench quickly even with tasks of low physical exertion. His coworkers have commented about his changing glove and boot sizes, which have increased at least 4 times since he joined the company 10 years ago. Physical examination is unremarkable except for blood pressure of 160/95 mm Hg, hyperhidrosis, noticeably large pores, hypertrichosis, widely spaced teeth, and prognathism. Which of the following best explains the patient’s clinical manifestations?
- A. Increased serum cortisol
- B. Increased thyroid-stimulating hormone
- C. Increased serum metanephrines
- D. Increased serum insulin-like growth factor 1 (IGF-1) (Correct Answer)
- E. Increased serum testosterone
Endocrine system (thyroid, adrenal, pancreas) Explanation: ***Increased serum insulin-like growth factor 1 (IGF-1)***
- Elevated **IGF-1** levels are indicative of **acromegaly**, a condition caused by excess growth hormone (GH) secretion, which explains the gradual changes in glove and boot sizes, prognathism, widely spaced teeth, and large pores.
- The symptoms of **profuse sweating**, **hypertrichosis**, **headaches**, and **hypertension** are common clinical manifestations of acromegaly due to the systemic effects of chronic GH excess.
*Increased serum cortisol*
- **Increased cortisol** (Cushing's syndrome) would present with central obesity, moon facies, buffalo hump, and striae, which are not described in the patient.
- While hypertension and hyperhidrosis can occur in Cushing's, the characteristic physical changes related to growth are absent.
*Increased thyroid-stimulating hormone*
- Elevated **TSH** suggests **hypothyroidism**, which would typically cause fatigue, weight gain, cold intolerance, and bradycardia, rather than profuse sweating and hypertension.
- **Hyperthyroidism** (low TSH, high thyroid hormones) can cause sweating and hypertension, but it would not explain the gradual increase in body and appendage size.
*Increased serum metanephrines*
- Elevated **metanephrines** are a hallmark of **pheochromocytoma**, which typically presents with paroxysmal episodes of hypertension, palpitations, and sweating.
- While sweating and hypertension are present, the absence of episodic symptoms and the long-term changes in body size make pheochromocytoma less likely.
*Increased serum testosterone*
- **Increased testosterone** in a male would typically lead to increased muscle mass, acne, and potentially male-pattern baldness, but not the specific skeletal and soft tissue growth patterns observed, such as increased shoe and glove size or prognathism.
- While some skin changes might occur, **hyperhidrosis** and the dramatic facial and extremity changes are not characteristic features of testosterone excess.
Endocrine system (thyroid, adrenal, pancreas) US Medical PG Question 3: A 15-year-old female presents to her family physician for an annual school physical exam and check-up. She is accompanied by her mother to the visit and is present in the exam room. The patient has no complaints, and she does not have any past medical problems. She takes no medications. The patient reports that she remains active, exercising 5 times a week, and eats a healthy and varied diet. Which of the following would be the best way for the physician to obtain a more in-depth social history, including sexual history and use of alcohol, tobacco, or recreational drugs?
- A. Disallow the mother to be present in the examination room throughout the entirety of the visit
- B. Give the patient a social history questionnaire to fill out in the exam room
- C. Ask the mother to step outside into the hall for a portion of the visit (Correct Answer)
- D. Ask the patient the questions directly, with her mother still in the exam room
- E. Speak softly to the patient so that the mother does not hear and the patient is not embarrassed
Endocrine system (thyroid, adrenal, pancreas) Explanation: ***Ask the mother to step outside into the hall for a portion of the visit***
- This approach allows the physician to speak with the adolescent **privately and confidentially**, which is crucial for obtaining sensitive information such as sexual history, drug use, and mental health concerns.
- Adolescents are more likely to disclose personal information when their parents are not present, fostering trust and ensuring **comprehensive history-taking** vital for their well-being.
*Disallow the mother to be present in the examination room throughout the entirety of the visit*
- This is an **overly restrictive** approach that might create tension or distrust between the physician, patient, and parent, especially at the start of the visit.
- While privacy is essential for sensitive topics, parental presence can be valuable for discussing general health, family history, and **treatment plans**, especially for younger adolescents.
*Give the patient a social history questionnaire to fill out in the exam room*
- While questionnaires can be useful for gathering basic information, they often **lack the nuance** of a direct conversation and may not prompt the patient to elaborate on sensitive issues.
- Furthermore, having the mother present while the patient fills out a questionnaire on sensitive topics still **compromises confidentiality** and may lead to incomplete or dishonest answers.
*Ask the patient the questions directly, with her mother still in the exam room*
- Asking sensitive questions with a parent present is **unlikely to yield truthful and complete answers**, as adolescents may feel embarrassed, judged, or fear parental disapproval.
- This approach compromises the **confidentiality** that is fundamental to building trust with adolescent patients.
*Speak softly to the patient so that the mother does not hear and the patient is not embarrassed*
- Speaking softly is **unprofessional** and still does not guarantee privacy, as the mother might still overhear parts of the conversation.
- This method also **fails to establish true confidentiality**, which is central to building rapport and encouraging open communication with adolescent patients about sensitive topics.
Endocrine system (thyroid, adrenal, pancreas) US Medical PG Question 4: A 60-year-old man comes to the emergency department because of recurrent episodes of fatigue, palpitations, nausea, and diaphoresis over the past 6 months. The episodes have become more frequent in the last 2 weeks and he has missed work several times because of them. His symptoms usually improve after he drinks some juice and rests. He has had a 2-kg (4.5-lb) weight gain in the past 6 months. He has a history of bipolar disorder, hypertension, and asthma. His sister has type 2 diabetes mellitus and his mother has a history of medullary thyroid carcinoma. His medications include lithium, hydrochlorothiazide, aspirin, and a budesonide inhaler. His temperature is 36.3°C (97.3°F), pulse is 92/min and regular, respirations are 20/min, and blood pressure is 118/65 mm Hg. Abdominal examination shows no abnormalities. Serum studies show:
Na+ 145 mEq/L
K+ 3.9 mEq/L
Cl- 103 mEq/L
Calcium 9.2 mg/dL
Glucose 88 mg/dL
Which of the following is the most appropriate next step in diagnosis?
- A. Corticotropin stimulation test
- B. Water deprivation test
- C. Oral glucose tolerance test
- D. 24-hour urine catecholamine test
- E. 72-hour fasting test (Correct Answer)
Endocrine system (thyroid, adrenal, pancreas) Explanation: **72-hour fasting test**
- The patient's symptoms (fatigue, palpitations, nausea, diaphoresis) that improve with eating (drinking juice) are highly suggestive of **hypoglycemia**, fitting **Whipple's triad**.
- A 72-hour fasting test is the gold standard for diagnosing **insulinoma**, a neuroendocrine tumor that causes endogenous hyperinsulinism and recurrent hypoglycemia.
*Corticotropin stimulation test*
- This test is used to diagnose **adrenal insufficiency** by evaluating the adrenal glands' response to ACTH.
- The patient's symptoms are inconsistent with adrenal insufficiency, and his blood pressure is stable, arguing against a hypotensive crisis.
*Water deprivation test*
- This test is used to diagnose **diabetes insipidus** by assessing the kidney's ability to concentrate urine.
- The patient's symptoms do not align with polyuria and polydipsia characteristic of diabetes insipidus.
*Oral glucose tolerance test*
- This test is primarily used to diagnose **diabetes mellitus** or impaired glucose tolerance.
- While helpful for assessing glucose metabolism, it is not the initial test for recurrent symptomatic hypoglycemia that improves with sugar intake.
*24-hour urine catecholamine test*
- This test is used to diagnose **pheochromocytoma**, a tumor that causes excessive catecholamine release.
- While palpitations and diaphoresis can occur, the improvement with glucose and lack of sustained hypertension make pheochromocytoma less likely.
Endocrine system (thyroid, adrenal, pancreas) US Medical PG Question 5: An investigator is studying a drug that acts on the thyroid hormone pathway. Levels of serum free T3 and T4 in healthy participants are measured before and after administration of the drug. After administration, there is a decrease in the average serum free T3 level, while the average serum free T4 level is increased compared to initial serum studies. Inhibition of which of the following is the most likely mechanism of action of this drug?
- A. Thyroid-stimulating hormone
- B. Follicular iodotyrosine deiodinase
- C. Follicular thyroid peroxidase
- D. Peripheral 5'-deiodinase (Correct Answer)
- E. Follicular thyroid proteases
Endocrine system (thyroid, adrenal, pancreas) Explanation: ***Peripheral 5'-deiodinase***
- Inhibition of **peripheral 5'-deiodinase** would decrease the conversion of **T4 to T3** in the periphery, resulting in lower **free T3** and higher **free T4** levels.
- This enzyme is crucial for activating T4 into the more potent T3, and its blockade explains the observed changes in hormone levels.
*Thyroid-stimulating hormone*
- Inhibition of **TSH** would lead to a decrease in the production and release of both **T3 and T4** from the thyroid gland.
- This contradicts the observed increase in **free T4** levels.
*Follicular iodotyrosine deiodinase*
- This enzyme is involved in recycling iodine from **monoiodotyrosine (MIT)** and **diiodotyrosine (DIT)** within the thyroid follicular cells, which is important for efficient thyroid hormone synthesis.
- Its inhibition would primarily affect iodine availability and synthesis, not directly lead to increased T4 and decreased T3 in the periphery.
*Follicular thyroid peroxidase*
- **Thyroid peroxidase (TPO)** is critical for the **iodination of tyrosine residues** on thyroglobulin and the **coupling of MIT and DIT** to form T3 and T4.
- Inhibition of TPO would decrease the synthesis of both **T3 and T4**, contrary to the observed increase in **free T4**.
*Follicular thyroid proteases*
- **Thyroid proteases** cleave thyroglobulin to release mature **T3 and T4** into the bloodstream.
- Inhibition of these proteases would lead to a decrease in the release of both **T3 and T4**, which does not align with the observed increase in **free T4**.
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