Free Internal Medicine Endocrinology and Metabolism Questions and Answers — Questions and Answers
Question 1: A 68-year-old male with a 10-year history of type 2 diabetes mellitus, hypertension, and a previous myocardial infarction is seen for follow-up. His current HbA1c is 8.2% on metformin 1000 mg twice daily. His eGFR is 70 mL/min/1.73m². According to current ADA guidelines, which of the following is the most appropriate medication to add to his regimen?
- Glipizide
- Empagliflozin (Correct answer)
- Sitagliptin
- Pioglitazone
Correct answer: Empagliflozin
For patients with type 2 diabetes and established atherosclerotic cardiovascular disease (ASCVD), guidelines strongly recommend adding an agent with proven cardiovascular benefit. SGLT2 inhibitors (like empagliflozin) and GLP-1 receptor agonists have demonstrated significant reductions in major adverse cardiovascular events. Sulfonylureas (glipizide) and DPP-4 inhibitors (sitagliptin) are generally considered to have a neutral effect on cardiovascular outcomes, while thiazolidinediones (pioglitazone) can carry a risk of worsening heart failure.
Question 2: A 52-year-old male is evaluated for resistant hypertension and is found to have a serum potassium of 3.2 mEq/L. Primary aldosteronism is suspected. What is the most appropriate initial screening test for this condition?
- 24-hour urine free cortisol
- Abdominal CT scan with adrenal protocol
- Morning plasma aldosterone concentration and plasma renin activity (Correct answer)
- Low-dose dexamethasone suppression test
Correct answer: Morning plasma aldosterone concentration and plasma renin activity
The Endocrine Society recommends screening for primary aldosteronism in patients with resistant hypertension and hypokalemia by measuring the morning plasma aldosterone concentration (PAC) and plasma renin activity (PRA) to calculate the aldosterone-to-renin ratio (ARR). An elevated ARR is a positive screen, prompting further confirmatory testing. An abdominal CT scan is used for subtype localization (e.g., adenoma vs. hyperplasia) after the biochemical diagnosis is established. The other tests are used to screen for Cushing's syndrome.
Question 3: An asymptomatic 72-year-old woman is found to have a serum calcium of 11.4 mg/dL (normal 8.6-10.3 mg/dL) on routine labs. Which of the following findings would most strongly suggest primary hyperparathyroidism as the cause of her hypercalcemia?
- A suppressed intact parathyroid hormone (PTH) level
- An elevated parathyroid hormone-related peptide (PTHrP) level
- A low 24-hour urine calcium excretion
- An elevated or inappropriately normal intact parathyroid hormone (PTH) level (Correct answer)
Correct answer: An elevated or inappropriately normal intact parathyroid hormone (PTH) level
Primary hyperparathyroidism is characterized by the autonomous production of PTH from one or more parathyroid glands. This leads to hypercalcemia, and the feedback loop is broken. Therefore, the hallmark finding is an elevated calcium level with a simultaneously elevated or inappropriately normal PTH level. A suppressed PTH would suggest a non-PTH-mediated cause of hypercalcemia, such as malignancy, which is often driven by PTHrP. Low urine calcium suggests familial hypocalciuric hypercalcemia (FHH).
Question 4: A 65-year-old man with a history of small cell lung cancer is admitted with confusion. His serum sodium is 118 mEq/L. He is clinically euvolemic. Further labs show serum osmolality of 250 mOsm/kg, urine osmolality of 400 mOsm/kg, and urine sodium of 50 mEq/L. Which of the following is the most appropriate immediate treatment?
- Intravenous infusion of 3% hypertonic saline (Correct answer)
- Oral fluid restriction to less than 1 liter per day
- Aggressive intravenous 0.9% normal saline infusion
- Administration of demeclocycline
Correct answer: Intravenous infusion of 3% hypertonic saline
This patient has severe, symptomatic hyponatremia due to the Syndrome of Inappropriate Antidiuretic Hormone (SIADH), a known paraneoplastic syndrome of small cell lung cancer. The presence of neurologic symptoms (confusion) necessitates urgent but controlled correction of the serum sodium to prevent further cerebral edema. The standard of care for this is an intravenous infusion of 3% hypertonic saline. Fluid restriction is the primary treatment for mild or asymptomatic SIADH, while 0.9% saline would worsen the hyponatremia. Demeclocycline is a second-line option for chronic management.
Question 5: A 78-year-old female is diagnosed with osteoporosis after a DEXA scan reveals a T-score of -2.9 at the femoral neck. Her medical history is significant for severe gastroesophageal reflux disease (GERD) and erosive esophagitis. Which of the following is the LEAST appropriate initial treatment for her osteoporosis?
- Intravenous zoledronic acid
- Subcutaneous denosumab
- Oral alendronate (Correct answer)
- Subcutaneous teriparatide
Correct answer: Oral alendronate
Oral bisphosphonates, such as alendronate, are known to cause significant upper gastrointestinal irritation, including esophagitis, esophageal erosions, and ulcers. Their use is relatively contraindicated in patients with pre-existing severe esophageal disease like erosive esophagitis. Safer and more appropriate alternatives in this patient would include non-oral options like intravenous zoledronic acid (an IV bisphosphonate), subcutaneous denosumab (a RANKL inhibitor), or subcutaneous teriparatide (an anabolic agent).
Question 6: A 34-year-old female is diagnosed with Graves' disease and is started on methimazole. Which of the following best describes the primary mechanism of action of this medication?
- Blocking the peripheral conversion of T4 to T3
- Inhibiting the release of pre-formed thyroid hormone
- Inhibiting the thyroid peroxidase enzyme, thus blocking hormone synthesis (Correct answer)
- Destroying thyroid follicular cells via antibody-dependent cytotoxicity
Correct answer: Inhibiting the thyroid peroxidase enzyme, thus blocking hormone synthesis
Thionamides, which include methimazole and propylthiouracil (PTU), work by inhibiting the thyroid peroxidase (TPO) enzyme. TPO is essential for catalyzing the organification of iodide and the coupling of iodotyrosines to form T4 and T3. By blocking this enzyme, thionamides effectively decrease the synthesis of new thyroid hormones. While PTU also weakly inhibits the peripheral conversion of T4 to T3, this is not the primary mechanism of action for methimazole.
Free Internal Medicine Endocrinology and Metabolism Questions and Answers
A 68-year-old male with a 10-year history of type 2 diabetes mellitus, hypertension, and a previous myocardial infarction is seen for follow-up.
His current HbA1c is 8.2% on metformin 1000 mg twice daily.
His eGFR is 70 mL/min/1.73m².
According to current ADA guidelines, which of the following is the most appropriate medication to add to his regimen?