Free Endocrinology Board Questions

Correct answer: A — Empagliflozin 10 mg daily

🩺 Why this is the correct answer: This patient has T2DM with HFrEF (LVEF 32%), stage 3b CKD (eGFR 38 mL/min/1.73m²), and HbA1c of 8.1% on metformin plus a sulfonylurea causing recurrent hypoglycemia. The pivotal question is selecting an agent that addresses both inadequate glycemic control AND the dominant cardiorenal comorbidities. SGLT2 inhibitors carry a CLASS I indication for HFrEF independent of T2DM status, supported by EMPEROR-Reduced (empagliflozin) and DAPA-HF (dapagliflozin), both demonstrating reduction in cardiovascular death and HF hospitalization. Empagliflozin is approved and indicated down to eGFR 20 for its HF/cardiorenal benefits; the reduced glycemic efficacy below eGFR 45 does not remove this indication. Furthermore, the sulfonylurea (glipizide) causing two hypoglycemic episodes per week should be discontinued simultaneously — adding an SGLT2i while deprescribing the sulfonylurea addresses both the hypoglycemia burden and the HFrEF. The 2024 ADA Standards of Care (Section 10) and 2022 AHA/ACC/HFSA Heart Failure Guidelines both endorse SGLT2i as first-line add-on therapy in this exact profile. SGLT2 inhibitors are potassium-neutral to mildly potassium-lowering, which is relevant given the patient's potassium of 4.8 mEq/L on sacubitril/valsartan — but this potassium value serves as a diagnostic discriminator against adding finerenone (not a listed option), not a contraindication to SGLT2i. 🚫 Why the other choices fail: Choice E: Dulaglutide, a GLP-1 receptor agonist, reduces ASCVD events (REWIND trial) and promotes weight loss, and is reasonable in obesity or ASCVD-predominant T2DM. However, GLP-1 RAs have NOT demonstrated reduction in HF hospitalization in dedicated trials and carry a Class IIb recommendation at best for HF. In a patient whose dominant comorbidity is HFrEF (LVEF 32%) with BNP 410 pg/mL, a GLP-1 RA is inferior to an SGLT2i for this specific indication per current guidelines. Choice B: Pioglitazone, a thiazolidinedione, causes fluid retention and worsening heart failure. It is contraindicated in NYHA class III/IV HF and strongly discouraged in HFrEF. Adding pioglitazone in a patient with LVEF 32% and BNP 410 pg/mL risks acute decompensation. Choice D: Sitagliptin, a DPP-4 inhibitor, is glucose-lowering and generally well-tolerated in CKD (dose-adjusted to 50 mg daily at eGFR 30–45). However, the SAVOR-TIMI 53 trial demonstrated a signal for increased HF hospitalization with saxagliptin, and while sitagliptin showed neutral HF outcomes (TECOS), DPP-4 inhibitors carry no positive HF benefit. In a patient with established HFrEF as the dominant risk driver, choosing sitagliptin over an SGLT2i is a missed opportunity to provide guideline-mandated, mortality-reducing therapy. Choice C: Insulin glargine would further intensify glycemic control but does not address HFrEF outcomes. More critically, adding basal insulin to an existing sulfonylurea regimen (without first discontinuing the sulfonylurea) markedly increases hypoglycemia risk in a 67-year-old patient already experiencing two episodes weekly. This choice represents escalation of regimen complexity without addressing the cardiorenal priority or the existing hypoglycemia safety concern. 💎 Board Pearl: SGLT2 inhibitors (empagliflozin, dapagliflozin) reduce HF hospitalization and cardiovascular death in HFrEF regardless of diabetes status; this cardiorenal benefit persists down to eGFR 20 and takes priority over GLP-1 RAs in the HFrEF-predominant T2DM patient. Concurrent deprescribing of the sulfonylurea is an integral part of the correct management step.

Correct answer: D — Methimazole for 4–6 weeks before RAI, then stop 3–5 days before treatment

🩺 Why this is the correct answer: This patient has overt Graves hyperthyroidism confirmed by suppressed TSH (<0.01 mIU/L), elevated free T4 (4.1 ng/dL), elevated free T3 (18.2 pg/mL), positive TRAb (6.8 IU/L), diffuse goiter, and high 24-hour RAIU (68%). He has elected radioiodine (RAI) therapy. Per ATA 2016 Hyperthyroidism Guidelines, pretreatment with an antithyroid drug (ATD) is recommended for patients who are at elevated cardiovascular risk or who have severe hyperthyroidism (free T4 >2–3× ULN, HR >120, or symptomatic disease) to reduce the risk of post-RAI thyroid storm or exacerbation. Methimazole — not PTU — is the preferred ATD in non-pregnant adults due to its superior hepatic safety profile. The ATD must be stopped 3–5 days before RAI to avoid radioprotection of the gland (iodine organification blockade would reduce RAI efficacy). This pre-treat/stop protocol is the guideline-endorsed strategy and is uniquely supported by the transaminase profile in this patient: AST 82 U/L and ALT 96 U/L are mildly elevated (<3× ULN), which is commonly seen in Graves hyperthyroidism itself and is not a contraindication to methimazole; however, these values reinforce the preference for methimazole over PTU, which carries a black-box warning for fulminant hepatotoxicity. 🚫 Why the other choices fail: Choice E: Propylthiouracil (PTU) is not preferred for pre-RAI preparation in a non-pregnant adult. The FDA issued a black-box warning for PTU-associated fulminant hepatic necrosis and liver failure. This patient already has mildly elevated transaminases (AST 82 U/L, ALT 96 U/L), making the hepatotoxic risk of PTU even less acceptable. PTU is reserved for T1 pregnancy and thyroid storm. Choosing PTU here reflects classic non-subspecialist reasoning and fails guideline-based pharmacologic selection. Choice A: Continuing methimazole through RAI administration is incorrect because methimazole blocks organification of iodine in thyroid follicular cells. If maintained during RAI, it competitively reduces iodine-131 uptake and retention, significantly lowering the absorbed radiation dose and decreasing the probability of achieving euthyroidism or ablation. The protocol requires discontinuation 3–5 days before RAI. Choice B: Propranolol monotherapy controls adrenergic symptoms but does not reduce thyroid hormone synthesis, lower circulating T3/T4 levels, or protect against post-RAI thyrotoxic surge. For a patient with free T4 of 4.1 ng/dL (>2× ULN), HR of 118 bpm, and significant weight loss, proceeding to RAI without ATD pre-treatment carries risk of worsening thyrotoxicosis. Symptom control alone is insufficient preparation. Choice C: Lithium carbonate inhibits thyroid hormone release and can transiently increase intrathyroidal iodine retention, occasionally used off-label to enhance RAI efficacy. However, it is not guideline-endorsed as a standard preparation strategy per ATA 2016. It carries a narrow therapeutic index with risks of nephrotoxicity, neurotoxicity, and cardiac arrhythmia. It would not be selected over a standard methimazole pre-treat/stop protocol in routine clinical practice. 💎 Board Pearl: Methimazole must be stopped 3–5 days before RAI (not continued through it) — ongoing organification blockade reduces iodine-131 uptake and ablation efficacy. PTU is avoided as pre-RAI preparation in non-pregnant adults due to black-box hepatotoxicity risk; mildly elevated transaminases in Graves disease (as seen here) further reinforce this preference.

Correct answer: D — Repeat 24-hour urine free cortisol collections timed to capture symptomatic episodes

🩺 Why this is the correct answer: This patient has persistently elevated late-night salivary cortisol on three separate occasions — a validated screening modality — in the setting of a clinically consistent syndrome, establishing biochemical evidence of hypercortisolism despite repeatedly normal 24-hour urine free cortisol (UFC) values and normal 1-mg DST results. This pattern is the hallmark of cyclic Cushing syndrome, in which cortisol hypersecretion is episodic: UFC and DST capture only "inactive" cycling phases and appear normal, whereas late-night salivary cortisol (reflecting nocturnal nadirs) may detect even brief hypersecretory bursts. The Endocrine Society 2008 Cushing Syndrome Diagnostic CPG (Nieman et al.) explicitly recognizes cyclic Cushing syndrome and recommends repeating urine collections timed to symptomatic ("active") periods when initial UFC results are discordant with other screening tests. Capturing UFC during a symptomatic episode is the necessary next step to document objectively elevated 24-hour cortisol output, fulfilling the requirement that at least two separate first-line tests be abnormal before proceeding to localization. Proceeding to MRI or measuring ACTH is premature because the biochemical diagnosis of Cushing syndrome has not yet been confirmed by a second concordant test modality. 🚫 Why the other choices fail: Choice B: Pituitary MRI is a localization tool, not a confirmatory diagnostic test. Per the 2008 Endocrine Society CPG, localization is inappropriate until biochemical confirmation of Cushing syndrome is established with two concordant abnormal first-line tests. A normal or incidental pituitary finding would be uninterpretable at this stage. Choice A: Dismissing the diagnosis based solely on two normal UFC values ignores the three consistently elevated late-night salivary cortisol results, which constitute positive screening by a validated first-line test. In cyclic Cushing syndrome, UFC may be normal during quiescent phases; two normal values do not exclude the diagnosis when another first-line modality is repeatedly abnormal. Choice E: The dexamethasone-CRH test is used to distinguish mild Cushing syndrome from pseudo-Cushing states (e.g., depression, alcohol use disorder) once Cushing syndrome is suspected but cannot be biochemically confirmed by standard tests. This patient does not yet meet the two-test threshold for confirmed hypercortisolism, and pseudo-Cushing is a less likely explanation for episodic symptoms with repeatedly elevated salivary cortisol; the dexamethasone-CRH test would precede localization, but comes after more straightforward documentation attempts in cyclic disease. Choice C: Measuring plasma ACTH determines ACTH-dependence and guides localization (pituitary vs. ectopic vs. adrenal), but this step is appropriate only after biochemical confirmation of Cushing syndrome. Performing ACTH before confirming hypercortisolism risks misinterpretation and is out of sequence per diagnostic guidelines. 💎 Board Pearl: In cyclic Cushing syndrome, 24-hour UFC and overnight DST may be repeatedly normal because sampling occurs during quiescent phases of the cycle; late-night salivary cortisol (averaged across multiple nights) is more sensitive for detecting episodic hypercortisolism, and UFC collections deliberately timed to symptomatic episodes are the recommended next step to achieve two concordant abnormal results before pursuing localization.