COMSAE PHASE 1 ASA 113
PRACTICE EXAMINATION
QUESTIONS WITH CORRECT
ANSWERS PLUS RATIONALES
2026/2027 EDITION WITH INSTANT
PDF DOWNLOAD
Question 1
A 24-year-old woman presents with fatigue, weight gain,
constipation, and cold intolerance. Laboratory studies show an
elevated thyroid-stimulating hormone (TSH) level and a
decreased free thyroxine (T4) level. Which of the following best
describes the underlying endocrine abnormality?
A. Increased thyroid hormone synthesis due to TSH receptor
stimulation
B. Decreased hypothalamic thyrotropin-releasing hormone
secretion
C. Primary failure of thyroid hormone synthesis
D. Excessive secretion of thyroid hormone from the thyroid gland
E. Increased conversion of T4 to triiodothyronine (T3)
Correct Answer: C. Primary failure of thyroid hormone
synthesis
Rationale: Primary hypothyroidism results from dysfunction of the
thyroid gland itself, causing decreased T4 production. The
,pituitary responds by increasing TSH secretion. Common causes
include autoimmune Hashimoto thyroiditis, iodine deficiency, and
thyroid ablation. The combination of high TSH and low free T4 is
characteristic of primary hypothyroidism.
Question 2
A 58-year-old man develops sudden weakness of the right face,
arm, and leg. He also has difficulty speaking and a right
homonymous hemianopia. Which cerebral artery is most likely
affected?
A. Left anterior cerebral artery
B. Right middle cerebral artery
C. Left middle cerebral artery
D. Right posterior cerebral artery
E. Left posterior cerebral artery
Correct Answer: C. Left middle cerebral artery
Rationale: The left middle cerebral artery supplies the lateral
frontal, parietal, and temporal regions, including the dominant
hemisphere language areas. An infarction can produce
contralateral face and upper-extremity weakness, aphasia, and
visual field deficits. Because the dominant hemisphere is usually
the left hemisphere, aphasia strongly suggests a left MCA lesion.
Question 3
A patient with severe diarrhea develops metabolic acidosis.
Laboratory testing shows a decreased serum bicarbonate
concentration and an increased respiratory rate. Which
,physiologic response primarily compensates for this acid-base
disturbance?
A. Increased renal bicarbonate excretion
B. Decreased pulmonary ventilation
C. Increased pulmonary carbon dioxide excretion
D. Increased hydrogen ion secretion by the lungs
E. Decreased renal ammonium production
Correct Answer: C. Increased pulmonary carbon dioxide
excretion
Rationale: Metabolic acidosis stimulates increased ventilation,
which decreases arterial PCO₂. This respiratory compensation
shifts the carbonic acid-bicarbonate equilibrium toward reduced
hydrogen ion concentration. The lungs respond rapidly, whereas
renal compensation develops more slowly.
Question 4
A 67-year-old man with long-standing hypertension develops
progressive exertional dyspnea. Echocardiography shows
concentric left ventricular hypertrophy. Which cellular adaptation
is responsible for the increased myocardial mass?
A. Hyperplasia of cardiomyocytes
B. Hypertrophy of cardiomyocytes
C. Metaplasia of cardiomyocytes
D. Dysplasia of cardiomyocytes
E. Increased cardiomyocyte apoptosis
Correct Answer: B. Hypertrophy of cardiomyocytes
, Rationale: Cardiac muscle cells have limited ability to divide.
Chronic pressure overload therefore produces hypertrophy rather
than hyperplasia. Increased workload stimulates enlargement of
individual cardiomyocytes and increased synthesis of contractile
proteins, producing concentric ventricular hypertrophy.
Question 5
A 19-year-old man has recurrent episodes of hemolytic anemia
after taking certain medications. Laboratory testing reveals
decreased activity of glucose-6-phosphate dehydrogenase.
Which biochemical process is most directly impaired?
A. ATP production through oxidative phosphorylation
B. Generation of NADPH through the pentose phosphate pathway
C. Conversion of pyruvate to lactate
D. Beta-oxidation of fatty acids
E. Ketone body synthesis
Correct Answer: B. Generation of NADPH through the pentose
phosphate pathway
Rationale: Glucose-6-phosphate dehydrogenase catalyzes the
first step of the pentose phosphate pathway and contributes to
production of NADPH. NADPH maintains glutathione in its
reduced form, protecting erythrocytes from oxidative damage.
Deficiency therefore predisposes to hemolysis during oxidative
stress.
Question 6
PRACTICE EXAMINATION
QUESTIONS WITH CORRECT
ANSWERS PLUS RATIONALES
2026/2027 EDITION WITH INSTANT
PDF DOWNLOAD
Question 1
A 24-year-old woman presents with fatigue, weight gain,
constipation, and cold intolerance. Laboratory studies show an
elevated thyroid-stimulating hormone (TSH) level and a
decreased free thyroxine (T4) level. Which of the following best
describes the underlying endocrine abnormality?
A. Increased thyroid hormone synthesis due to TSH receptor
stimulation
B. Decreased hypothalamic thyrotropin-releasing hormone
secretion
C. Primary failure of thyroid hormone synthesis
D. Excessive secretion of thyroid hormone from the thyroid gland
E. Increased conversion of T4 to triiodothyronine (T3)
Correct Answer: C. Primary failure of thyroid hormone
synthesis
Rationale: Primary hypothyroidism results from dysfunction of the
thyroid gland itself, causing decreased T4 production. The
,pituitary responds by increasing TSH secretion. Common causes
include autoimmune Hashimoto thyroiditis, iodine deficiency, and
thyroid ablation. The combination of high TSH and low free T4 is
characteristic of primary hypothyroidism.
Question 2
A 58-year-old man develops sudden weakness of the right face,
arm, and leg. He also has difficulty speaking and a right
homonymous hemianopia. Which cerebral artery is most likely
affected?
A. Left anterior cerebral artery
B. Right middle cerebral artery
C. Left middle cerebral artery
D. Right posterior cerebral artery
E. Left posterior cerebral artery
Correct Answer: C. Left middle cerebral artery
Rationale: The left middle cerebral artery supplies the lateral
frontal, parietal, and temporal regions, including the dominant
hemisphere language areas. An infarction can produce
contralateral face and upper-extremity weakness, aphasia, and
visual field deficits. Because the dominant hemisphere is usually
the left hemisphere, aphasia strongly suggests a left MCA lesion.
Question 3
A patient with severe diarrhea develops metabolic acidosis.
Laboratory testing shows a decreased serum bicarbonate
concentration and an increased respiratory rate. Which
,physiologic response primarily compensates for this acid-base
disturbance?
A. Increased renal bicarbonate excretion
B. Decreased pulmonary ventilation
C. Increased pulmonary carbon dioxide excretion
D. Increased hydrogen ion secretion by the lungs
E. Decreased renal ammonium production
Correct Answer: C. Increased pulmonary carbon dioxide
excretion
Rationale: Metabolic acidosis stimulates increased ventilation,
which decreases arterial PCO₂. This respiratory compensation
shifts the carbonic acid-bicarbonate equilibrium toward reduced
hydrogen ion concentration. The lungs respond rapidly, whereas
renal compensation develops more slowly.
Question 4
A 67-year-old man with long-standing hypertension develops
progressive exertional dyspnea. Echocardiography shows
concentric left ventricular hypertrophy. Which cellular adaptation
is responsible for the increased myocardial mass?
A. Hyperplasia of cardiomyocytes
B. Hypertrophy of cardiomyocytes
C. Metaplasia of cardiomyocytes
D. Dysplasia of cardiomyocytes
E. Increased cardiomyocyte apoptosis
Correct Answer: B. Hypertrophy of cardiomyocytes
, Rationale: Cardiac muscle cells have limited ability to divide.
Chronic pressure overload therefore produces hypertrophy rather
than hyperplasia. Increased workload stimulates enlargement of
individual cardiomyocytes and increased synthesis of contractile
proteins, producing concentric ventricular hypertrophy.
Question 5
A 19-year-old man has recurrent episodes of hemolytic anemia
after taking certain medications. Laboratory testing reveals
decreased activity of glucose-6-phosphate dehydrogenase.
Which biochemical process is most directly impaired?
A. ATP production through oxidative phosphorylation
B. Generation of NADPH through the pentose phosphate pathway
C. Conversion of pyruvate to lactate
D. Beta-oxidation of fatty acids
E. Ketone body synthesis
Correct Answer: B. Generation of NADPH through the pentose
phosphate pathway
Rationale: Glucose-6-phosphate dehydrogenase catalyzes the
first step of the pentose phosphate pathway and contributes to
production of NADPH. NADPH maintains glutathione in its
reduced form, protecting erythrocytes from oxidative damage.
Deficiency therefore predisposes to hemolysis during oxidative
stress.
Question 6
