ITE Endocrinology and Metabolism 5 — Questions and Answers
Question 1: A 48-year-old woman with type 2 diabetes on metformin and linagliptin develops worsening renal function (eGFR now 22 mL/min). Which medication adjustment is most appropriate?
- Discontinue metformin; continue linagliptin (Correct answer)
- Discontinue both metformin and linagliptin
- Continue both at reduced doses
- Switch linagliptin to sitagliptin
Correct answer: Discontinue metformin; continue linagliptin
Metformin is contraindicated when eGFR <30 mL/min; linagliptin, unlike other DPP-4 inhibitors, is primarily excreted via bile and requires no renal dose adjustment even in severe CKD.
Question 2: A 35-year-old man has hypertension, hypokalemia, and metabolic alkalosis. Plasma renin activity is markedly elevated, as is aldosterone. CT shows a 3 cm right renal artery mass. What is the most likely diagnosis?
- Primary hyperaldosteronism (Conn syndrome)
- Juxtaglomerular cell tumor (reninoma) (Correct answer)
- Pheochromocytoma
- Adrenocortical carcinoma
Correct answer: Juxtaglomerular cell tumor (reninoma)
A juxtaglomerular cell tumor (reninoma) secretes renin autonomously, causing secondary hyperaldosteronism with high renin; in primary hyperaldosteronism, renin would be suppressed.
Question 3: A 68-year-old woman with osteoporosis and a T-score of −3.0 at the hip has been on denosumab for 3 years. She asks about stopping therapy. What is the most important risk to counsel her about?
- Rebound hypercalcemia
- Rapid bone loss and increased vertebral fracture risk upon discontinuation (Correct answer)
- Jaw osteonecrosis upon stopping
- Development of monoclonal gammopathy
Correct answer: Rapid bone loss and increased vertebral fracture risk upon discontinuation
Denosumab discontinuation causes a rebound increase in bone turnover markers and rapid bone loss, significantly increasing vertebral fracture risk; transition to a bisphosphonate is recommended before stopping.
Question 4: A 52-year-old man presents with increased hat and shoe size over 5 years, jaw prominence, and hyperhidrosis. Random GH is 12 ng/mL. What is the confirmatory test for acromegaly?
- IGF-1 level alone
- GH after oral glucose tolerance test (OGTT) (Correct answer)
- 24-hour urine GH
- Insulin tolerance test (ITT)
Correct answer: GH after oral glucose tolerance test (OGTT)
In acromegaly, GH fails to suppress to <1 ng/mL after 75 g oral glucose load (OGTT); this is the gold-standard confirmatory test because random GH levels fluctuate.
Question 5: A 29-year-old woman presents with weakness, hyperpigmentation, salt craving, and orthostatic hypotension. Labs show Na 128 mEq/L, K 5.8 mEq/L, and glucose 62 mg/dL. ACTH stimulation test shows a peak cortisol of 10 mcg/dL at 60 minutes. What is the most likely diagnosis?
- Secondary adrenal insufficiency
- Primary adrenal insufficiency (Addison's disease) (Correct answer)
- Cushing syndrome
- Congenital adrenal hyperplasia (non-classic)
Correct answer: Primary adrenal insufficiency (Addison's disease)
Primary adrenal insufficiency (Addison's disease) is characterized by loss of both cortisol and aldosterone, causing hyponatremia, hyperkalemia, hyperpigmentation (elevated ACTH), and a blunted cortisol response to ACTH stimulation.
Question 6: A 45-year-old woman presents with palpitations, tremor, and a painless diffuse goiter. TSH is 0.01 mIU/L, free T4 is 3.2 ng/dL. TSH receptor antibodies are positive. She wants the most definitive long-term cure. What is the best option?
- Methimazole for 12–18 months
- Radioactive iodine ablation
- Total thyroidectomy (Correct answer)
- Beta-blocker monotherapy
Correct answer: Total thyroidectomy
Total thyroidectomy provides the most immediate and definitive cure for Graves' disease and is preferred when the patient desires rapid, definitive resolution; RAI is effective but slower and may worsen ophthalmopathy.
Question 7: A 38-year-old man with MEN1 syndrome undergoes screening. He is found to have a fasting gastrin level of 890 pg/mL (normal <100) and multiple small duodenal ulcers. What syndrome is he most likely developing?
- VIPoma syndrome (Verner-Morrison)
- Zollinger-Ellison syndrome (gastrinoma) (Correct answer)
- Glucagonoma syndrome
- Insulinoma-associated hypoglycemia
Correct answer: Zollinger-Ellison syndrome (gastrinoma)
Markedly elevated gastrin causing refractory peptic ulcer disease is diagnostic of Zollinger-Ellison syndrome (gastrinoma), which occurs in 20–30% of MEN1 patients and is the most common functional pancreatic tumor in MEN1.
ITE Endocrinology and Metabolism 5
A 48-year-old woman with type 2 diabetes on metformin and linagliptin develops worsening renal function (eGFR now 22 mL/min).
Which medication adjustment is most appropriate?