American Board of Internal Medicine
Endocrinology, Diabetes, and Metabolism
Certification Exam Questions and Correct Answers
(Verified Answers) Plus Rationales 2026 Q&A |
Instant Download Pdf
1. A 55-year-old man presents with fatigue, weight gain, and cold
intolerance. On exam, he has dry skin and delayed relaxation of deep
tendon reflexes. Lab results show TSH 12 µIU/mL (normal 0.5–5) and
free T4 low. What is the most likely diagnosis?
A) Subclinical hypothyroidism
B) Secondary hypothyroidism
C) Primary hypothyroidism
D) Euthyroid sick syndrome
Answer: C) Primary hypothyroidism
Rationale: Elevated TSH with low free T4 indicates primary
hypothyroidism, where the thyroid gland itself is underactive. Delayed
reflex relaxation is a classic physical sign.
2. A 30-year-old woman presents with heat intolerance, palpitations,
and weight loss. Labs show suppressed TSH and elevated free T4.
Radioactive iodine uptake is diffusely increased. What is the most
likely diagnosis?
A) Toxic multinodular goiter
B) Graves disease
,C) Subacute thyroiditis
D) Euthyroid sick syndrome
Answer: B) Graves disease
Rationale: Diffuse radioactive iodine uptake with suppressed TSH and
hyperthyroidism symptoms is consistent with Graves disease, an
autoimmune hyperthyroidism.
3. Which of the following antibodies is most specific for Graves
disease?
A) Anti-TPO
B) Anti-thyroglobulin
C) TSH receptor antibodies
D) Anti-microsomal
Answer: C) TSH receptor antibodies
Rationale: TSH receptor antibodies (TRAb) are highly specific for Graves
disease, whereas anti-TPO and anti-thyroglobulin are more common in
Hashimoto thyroiditis.
4. A patient with type 2 diabetes is started on a GLP-1 receptor
agonist. What is the main mechanism of action?
A) Increases renal glucose excretion
B) Stimulates insulin secretion in a glucose-dependent manner
C) Inhibits hepatic gluconeogenesis
D) Sensitizes peripheral tissues to insulin
Answer: B) Stimulates insulin secretion in a glucose-dependent
manner
Rationale: GLP-1 receptor agonists enhance glucose-dependent insulin
,secretion, slow gastric emptying, and reduce appetite, which improves
glycemic control.
5. A 65-year-old man with a history of osteoporosis presents with
vertebral fractures. Labs reveal serum calcium normal, phosphate
low, PTH elevated, and vitamin D deficiency. What is the most likely
cause of secondary hyperparathyroidism?
A) Primary hyperparathyroidism
B) Chronic kidney disease
C) Vitamin D deficiency
D) Malignancy
Answer: C) Vitamin D deficiency
Rationale: Low vitamin D leads to reduced calcium absorption, causing
compensatory PTH elevation, known as secondary hyperparathyroidism.
6. Which of the following is the first-line therapy for symptomatic
primary hyperparathyroidism in a patient without contraindications?
A) Cinacalcet
B) Bisphosphonates
C) Parathyroidectomy
D) Observation
Answer: C) Parathyroidectomy
Rationale: Surgery is the definitive treatment for primary
hyperparathyroidism in symptomatic patients or those meeting specific
biochemical criteria.
, 7. A 42-year-old woman presents with progressive proximal muscle
weakness, weight gain, and easy bruising. Labs show elevated 24-hour
urine free cortisol. What is the most likely diagnosis?
A) Addison disease
B) Cushing syndrome
C) Hypothyroidism
D) Hyperaldosteronism
Answer: B) Cushing syndrome
Rationale: Features of central obesity, proximal muscle weakness, easy
bruising, and hypercortisolism indicate Cushing syndrome.
8. In the evaluation of Cushing syndrome, which test is most
appropriate for initial screening?
A) 1 mg overnight dexamethasone suppression test
B) Plasma ACTH alone
C) 24-hour urinary metanephrines
D) Serum aldosterone
Answer: A) 1 mg overnight dexamethasone suppression test
Rationale: The overnight dexamethasone suppression test is a sensitive
initial screen for hypercortisolism.
9. Which of the following is the most common cause of endogenous
Cushing syndrome?
A) Adrenal adenoma
B) Pituitary adenoma (Cushing disease)
C) Ectopic ACTH production
D) Exogenous corticosteroids
Endocrinology, Diabetes, and Metabolism
Certification Exam Questions and Correct Answers
(Verified Answers) Plus Rationales 2026 Q&A |
Instant Download Pdf
1. A 55-year-old man presents with fatigue, weight gain, and cold
intolerance. On exam, he has dry skin and delayed relaxation of deep
tendon reflexes. Lab results show TSH 12 µIU/mL (normal 0.5–5) and
free T4 low. What is the most likely diagnosis?
A) Subclinical hypothyroidism
B) Secondary hypothyroidism
C) Primary hypothyroidism
D) Euthyroid sick syndrome
Answer: C) Primary hypothyroidism
Rationale: Elevated TSH with low free T4 indicates primary
hypothyroidism, where the thyroid gland itself is underactive. Delayed
reflex relaxation is a classic physical sign.
2. A 30-year-old woman presents with heat intolerance, palpitations,
and weight loss. Labs show suppressed TSH and elevated free T4.
Radioactive iodine uptake is diffusely increased. What is the most
likely diagnosis?
A) Toxic multinodular goiter
B) Graves disease
,C) Subacute thyroiditis
D) Euthyroid sick syndrome
Answer: B) Graves disease
Rationale: Diffuse radioactive iodine uptake with suppressed TSH and
hyperthyroidism symptoms is consistent with Graves disease, an
autoimmune hyperthyroidism.
3. Which of the following antibodies is most specific for Graves
disease?
A) Anti-TPO
B) Anti-thyroglobulin
C) TSH receptor antibodies
D) Anti-microsomal
Answer: C) TSH receptor antibodies
Rationale: TSH receptor antibodies (TRAb) are highly specific for Graves
disease, whereas anti-TPO and anti-thyroglobulin are more common in
Hashimoto thyroiditis.
4. A patient with type 2 diabetes is started on a GLP-1 receptor
agonist. What is the main mechanism of action?
A) Increases renal glucose excretion
B) Stimulates insulin secretion in a glucose-dependent manner
C) Inhibits hepatic gluconeogenesis
D) Sensitizes peripheral tissues to insulin
Answer: B) Stimulates insulin secretion in a glucose-dependent
manner
Rationale: GLP-1 receptor agonists enhance glucose-dependent insulin
,secretion, slow gastric emptying, and reduce appetite, which improves
glycemic control.
5. A 65-year-old man with a history of osteoporosis presents with
vertebral fractures. Labs reveal serum calcium normal, phosphate
low, PTH elevated, and vitamin D deficiency. What is the most likely
cause of secondary hyperparathyroidism?
A) Primary hyperparathyroidism
B) Chronic kidney disease
C) Vitamin D deficiency
D) Malignancy
Answer: C) Vitamin D deficiency
Rationale: Low vitamin D leads to reduced calcium absorption, causing
compensatory PTH elevation, known as secondary hyperparathyroidism.
6. Which of the following is the first-line therapy for symptomatic
primary hyperparathyroidism in a patient without contraindications?
A) Cinacalcet
B) Bisphosphonates
C) Parathyroidectomy
D) Observation
Answer: C) Parathyroidectomy
Rationale: Surgery is the definitive treatment for primary
hyperparathyroidism in symptomatic patients or those meeting specific
biochemical criteria.
, 7. A 42-year-old woman presents with progressive proximal muscle
weakness, weight gain, and easy bruising. Labs show elevated 24-hour
urine free cortisol. What is the most likely diagnosis?
A) Addison disease
B) Cushing syndrome
C) Hypothyroidism
D) Hyperaldosteronism
Answer: B) Cushing syndrome
Rationale: Features of central obesity, proximal muscle weakness, easy
bruising, and hypercortisolism indicate Cushing syndrome.
8. In the evaluation of Cushing syndrome, which test is most
appropriate for initial screening?
A) 1 mg overnight dexamethasone suppression test
B) Plasma ACTH alone
C) 24-hour urinary metanephrines
D) Serum aldosterone
Answer: A) 1 mg overnight dexamethasone suppression test
Rationale: The overnight dexamethasone suppression test is a sensitive
initial screen for hypercortisolism.
9. Which of the following is the most common cause of endogenous
Cushing syndrome?
A) Adrenal adenoma
B) Pituitary adenoma (Cushing disease)
C) Ectopic ACTH production
D) Exogenous corticosteroids
