MD Medical Doctor General 3 — Questions and Answers
Question 1: A 45-year-old woman presents with weight gain, cold intolerance, constipation, and a TSH of 12 mIU/L with low free T4. What is the most appropriate treatment?
- Liothyronine (T3) supplementation
- Levothyroxine (T4) replacement (Correct answer)
- Methimazole
- Radioactive iodine ablation
Correct answer: Levothyroxine (T4) replacement
Primary hypothyroidism is treated with levothyroxine (synthetic T4), which is peripherally converted to the active T3 hormone.
Question 2: Which drug class is contraindicated in a patient with bilateral renal artery stenosis who has hypertension?
- Beta-blockers
- Calcium channel blockers
- ACE inhibitors (Correct answer)
- Thiazide diuretics
Correct answer: ACE inhibitors
ACE inhibitors block angiotensin II–mediated efferent arteriolar constriction, which is essential to maintain GFR in bilateral renal artery stenosis, causing acute kidney injury.
Question 3: A 25-year-old presents with episodic hypertension, headache, diaphoresis, and palpitations. Urine metanephrines are markedly elevated. What is the likely diagnosis?
- Primary hyperaldosteronism
- Pheochromocytoma (Correct answer)
- Carcinoid syndrome
- Essential hypertension
Correct answer: Pheochromocytoma
Pheochromocytoma is a catecholamine-secreting adrenal tumor presenting with episodic hypertension, headache, diaphoresis, and palpitations, diagnosed by elevated urine/plasma metanephrines.
Question 4: A patient with rheumatoid arthritis on long-term methotrexate therapy should receive which supplementation to prevent a common adverse effect?
- Vitamin B12
- Folic acid (Correct answer)
- Vitamin D
- Iron
Correct answer: Folic acid
Methotrexate inhibits dihydrofolate reductase; folic acid supplementation reduces the risk of mucositis, hepatotoxicity, and cytopenias without significantly reducing efficacy.
Question 5: A 70-year-old man presents with urinary frequency, hesitancy, and a post-void residual of 200 mL. Digital rectal exam shows a smooth, enlarged prostate. PSA is 2.8 ng/mL. What is the most likely diagnosis?
- Prostate cancer
- Benign prostatic hyperplasia (Correct answer)
- Prostatitis
- Bladder cancer
Correct answer: Benign prostatic hyperplasia
BPH causes obstructive lower urinary tract symptoms with a smooth, uniformly enlarged prostate and elevated post-void residual without PSA dramatically elevated.
Question 6: Which cell type is primarily responsible for producing antibodies (immunoglobulins)?
- T helper cells
- Natural killer cells
- Plasma cells (Correct answer)
- Dendritic cells
Correct answer: Plasma cells
Plasma cells are terminally differentiated B lymphocytes that produce large quantities of antigen-specific immunoglobulins.
Question 7: A 60-year-old smoker presents with hemoptysis, weight loss, and a central lung mass on chest X-ray. Biopsy shows small cells with neuroendocrine features. Which paraneoplastic syndrome is most associated with this tumor?
- Hypercalcemia of malignancy
- SIADH causing hyponatremia (Correct answer)
- Erythrocytosis
- Acanthosis nigricans
Correct answer: SIADH causing hyponatremia
Small cell lung cancer frequently produces ectopic ADH (SIADH) causing hyponatremia; it also produces ACTH but SIADH is the most common paraneoplastic syndrome.
MD Medical Doctor General 3
A 45-year-old woman presents with weight gain, cold intolerance, constipation, and a TSH of 12 mIU/L with low free T4.
What is the most appropriate treatment?