Endocrinology Practice Questions

Q: Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is diagnosed by all EXCEPT:

Normal blood urea nitrogen. **Explanation:** The diagnosis of **SIADH** is based on the **Bartter-Schwartz criteria**. It is a condition of "euvolemic hyponatremia" where excessive ADH leads to water retention and secondary solute loss [1]. **Why Option C is the correct answer (The Exception):** In SIADH, the expansion of total body water leads to a **dilutional effect** and increased renal clearance of urea. Therefore, a characteristic finding in SIADH is a **Low Blood Urea Nitrogen (BUN <10 mg/dL)** and low serum uric acid. A "Normal" BUN (typically 10–20 mg/dL) actually points away from SIADH and suggests other causes of hyponatremia or underlying renal impairment. **Analysis of Incorrect Options:** * **A & B (Hyponatremia & Decreased Serum Osmolality):** These are the hallmarks of SIADH [2]. Excessive water reabsorption dilutes the extracellular fluid, leading to hypotonic hyponatremia (Serum Na <135 mEq/L and Osmolality <280 mOsm/kg). * **D (Normal Thyroid Function):** To diagnose SIADH, one must **exclude** other causes of euvolemic hyponatremia. Both hypothyroidism and adrenal insufficiency (glucocorticoid deficiency) can mimic SIADH; thus, normal thyroid and adrenal functions are mandatory diagnostic requirements [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Urine Findings:** Urine osmolality is inappropriately high (>100 mOsm/kg, often > serum) and urine sodium is high (>40 mEq/L) due to the absence of hypovolemia. * **Volume Status:** Patients are clinically **euvolemic** (no edema, no JVP elevation) [2]. * **Treatment:** Fluid restriction is the first-line treatment. For severe cases, Vaptans (ADH antagonists) or hypertonic saline may be used. * **Caution:** Rapid correction of hyponatremia can lead to **Osmotic Demyelination Syndrome (Central Pontine Myelinolysis).**

Q: Conn's syndrome is characterized by:

Hyperaldosteronism. **Explanation:** **Conn’s Syndrome** (Primary Hyperaldosteronism) is a condition characterized by the autonomous overproduction of aldosterone from the adrenal cortex, most commonly due to an aldosterone-secreting adrenal adenoma (60-70%) or bilateral adrenal hyperplasia. **Why Option D is Correct:** Aldosterone acts on the distal convoluted tubules and collecting ducts of the kidney to promote **sodium and water reabsorption** and **potassium/hydrogen ion excretion**. Consequently, Conn’s syndrome presents with the classic triad of **Hypertension** (due to volume expansion), **Hypokalemia** (leading to muscle weakness), and **Metabolic Alkalosis**. **Why Other Options are Incorrect:** * **A. Hyperinsulinism:** This refers to excessive insulin levels, typically seen in Insulinomas or Nesidioblastosis, leading to hypoglycemia. * **B. Hyperthyroidism:** This involves excessive thyroid hormone (T3/T4) production (e.g., Graves' disease), presenting with tachycardia, weight loss, and heat intolerance. * **C. Hypoadrenalism:** This is the opposite of Conn’s; conditions like Addison’s disease involve a deficiency of adrenal hormones (cortisol and aldosterone), leading to hypotension and hyperkalemia. **High-Yield Clinical Pearls for NEET-PG:** * **Screening Test:** Plasma Aldosterone Concentration (PAC) to Plasma Renin Activity (PRA) ratio. A **PAC:PRA ratio > 20-30** is highly suggestive. * **Confirmatory Test:** Saline infusion test (failure to suppress aldosterone) or Oral Salt Loading test. * **Drug of Choice:** **Spironolactone** (Aldosterone antagonist) is used for bilateral hyperplasia or as preoperative medical management. * **Key Association:** Conn’s syndrome is a secondary cause of hypertension where **plasma renin levels are characteristically low** (suppressed by volume expansion).

Q: What is the most common presentation of sick euthyoid state?

Low T3 with normal T4. **Explanation:** **Sick Euthyroid Syndrome (SES)**, also known as Non-Thyroidal Illness Syndrome (NTIS), refers to alterations in thyroid function tests seen in patients with severe systemic illness (e.g., sepsis, trauma, or starvation) in the absence of pre-existing thyroid disease. **Why Option A is Correct:** The most common and earliest finding in SES is a **Low T3 level with a normal T4 and normal TSH**. This occurs due to the inhibition of the enzyme **5’-deiodinase**, which normally converts T4 (pro-hormone) to T3 (active hormone) in peripheral tissues [1]. Instead, T4 is diverted to form **Reverse T3 (rT3)**, which is metabolically inactive. **Analysis of Incorrect Options:** * **Option B (Low T3, Low T4):** This is seen in **severe or prolonged illness**. As the severity of the systemic disease increases, T4 levels also drop (Low T4 syndrome), which is a poor prognostic indicator. However, it is not the *most common* initial presentation. * **Option C & D:** These patterns are not characteristic of SES. High T4 is rarely seen unless there is an inhibition of T4 uptake by hepatocytes (transiently in acute illness), and high T3 is never a feature of sick euthyroid state. **NEET-PG High-Yield Pearls:** 1. **Hallmark:** Low T3, High Reverse T3 (rT3), and Normal TSH. 2. **TSH Paradox:** Although T3 is low, TSH remains normal (or mildly low) because the pituitary-thyroid axis is "reset" during stress. 3. **Management:** Do **NOT** treat with thyroxine. The condition resolves spontaneously once the underlying systemic illness is treated. 4. **Prognosis:** A very low T4 level in a critically ill patient is associated with a high mortality rate.

Q: What is the confirmatory test for Cushing's disease?

Bilateral inferior petrosal sinus sampling. ### Explanation The diagnostic approach to Cushing’s syndrome follows a strict hierarchy: first, confirm hypercortisolism; second, determine if it is ACTH-dependent; and third, localize the source [1]. **Why Bilateral Inferior Petrosal Sinus Sampling (BIPSS) is correct:** BIPSS is the **gold standard** for differentiating between a pituitary source (Cushing’s Disease) and an ectopic source of ACTH. It involves measuring ACTH levels in the venous drainage of the pituitary gland compared to peripheral blood. A central-to-peripheral ACTH ratio of **≥2:1 (basal)** or **≥3:1 (after CRH stimulation)** confirms Cushing’s disease with high sensitivity and specificity. It is typically performed when biochemical tests suggest a pituitary source but MRI is inconclusive or negative. **Analysis of Incorrect Options:** * **B & C (24-hour Urine Free Cortisol & Overnight DST):** These are **screening tests** used to establish the presence of hypercortisolism (Cushing’s Syndrome) [1]. They do not differentiate the underlying cause (pituitary vs. adrenal vs. ectopic). * **A (High-dose Dexamethasone Suppression Test - HDDST):** Historically used to distinguish Cushing’s disease from ectopic ACTH, HDDST is no longer considered the "confirmatory" test due to its lower accuracy compared to BIPSS and modern imaging [1]. **NEET-PG High-Yield Pearls:** * **Screening:** Best initial test is either Late-night salivary cortisol, 24-hr urinary free cortisol, or Low-dose DST [1]. * **Localization:** If ACTH is high (>20 pg/mL), it is ACTH-dependent [2]. Perform MRI Brain. * **The "Rule of 6mm":** If MRI shows a pituitary adenoma **>6 mm**, Cushing’s disease is confirmed. If <6 mm or MRI is normal, **BIPSS** is the next step to confirm the source. * **Most common cause** of endogenous Cushing’s syndrome: Cushing’s Disease (Pituitary adenoma).

Q: A 33-year-old man complains of a tingling sensation in his hands for several months, which occasionally awakens him during sleep. The patient has noticed he has gained weight and no longer wears his wedding ring as it has become too tight. Upon examination, the patient is noted to be sweating while speaking and has a prominent jaw, furrowed tongue, and large hands. His blood pressure is 142/91 mmHg. What is the most appropriate investigation?

Glucose tolerance test. ### Explanation The clinical presentation of weight gain, tightening of rings (soft tissue swelling), prominent jaw (prognathism), furrowed tongue (macroglossia), and excessive sweating is classic for **Acromegaly**, caused by excessive Growth Hormone (GH) secretion. The tingling in the hands suggests **Carpal Tunnel Syndrome**, a common complication of acromegaly due to soft tissue overgrowth compressing the median nerve. #### Why Option B is Correct The **Oral Glucose Tolerance Test (OGTT) with GH measurement** is the **gold standard confirmatory test** for acromegaly [1]. In a healthy individual, a high glucose load (75g) suppresses GH levels to <1 ng/mL. In acromegaly, there is a failure to suppress GH, or even a paradoxical rise, confirming autonomous secretion [1]. While Serum IGF-1 is the best *screening* test, OGTT is the definitive biochemical investigation [1]. #### Why Other Options are Incorrect * **A. MRI scan of the pituitary:** This is the investigation of choice for *localization* of the tumor (usually a macroadenoma) [1]. However, biochemical confirmation (OGTT) must always precede imaging to avoid incidentaloma findings [2]. * **C. Growth hormone levels:** A single random GH measurement is unreliable because GH is secreted in pulsatile bursts and has a short half-life. * **D. Serum prolactin levels:** While 25-30% of GH-secreting tumors also secrete prolactin (mammosomatotrophs), it is not the diagnostic test for acromegaly [1]. #### NEET-PG High-Yield Pearls * **Best Screening Test:** Serum IGF-1 (reflects GH activity over 24 hours) [1]. * **Best Confirmatory Test:** OGTT (GH suppression test) [1]. * **Most Common Cause of Death:** Cardiovascular disease (Cardiomyopathy/Hypertension). * **Associated Cancer Risk:** Increased risk of **Colonic Polyps and Adenocarcinoma**; screening colonoscopy is recommended [1]. * **Visual Defect:** Bitemporal hemianopia (due to optic chiasm compression) [2].

Question 1

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is diagnosed by all EXCEPT:

Accepted Answer

Normal blood urea nitrogen

Answer

Hyponatremia

Answer

Decreased serum osmolality (< 280 mosm/kg)

Answer

Normal thyroid function

Question 2

A 29-year-old person, known diabetic on oral hypoglycemic agents for 3 years, has lost weight and never had diabetic ketoacidosis. His grandfather is diabetic, but his father is not. Which of the following is the likely diagnosis?

Accepted Answer

Diabetes Mellitus type II

Answer

Maturity Onset Diabetes of the Young (MODY)

Answer

Diabetes Mellitus type I

Answer

Pancreatic diabetes

Question 3

Conn's syndrome is characterized by:

Accepted Answer

Hyperaldosteronism

Answer

Hyperinsulinism

Answer

Hyperthyroidism

Answer

Hypoadrenalism

Question 4

A 63-year-old woman with well-controlled Type II diabetes mellitus presents with peripheral neuropathy in the feet and non-proliferative retinopathy. Urinalysis is positive for proteinuria. Which of the following treatments is most likely to attenuate the course of renal disease?

Accepted Answer

ACE inhibitors

Answer

Calcium channel blockers

Answer

Hepatic hydroxymethylglutaryl-coenzyme A (HMG-CoA) inhibitors

Answer

Dietary carbohydrate restriction

Question 5

What is the most common presentation of sick euthyoid state?

Accepted Answer

Low T3 with normal T4

Answer

Low T3 with low T4

Answer

Low T3 with high T4

Answer

High T3 with high T4

Question 6

Insulin sensitivity increases with the following treatments except:

Accepted Answer

Fasting

Answer

Metformin

Answer

Acarbose

Answer

Exercise

Question 7

For the following causes of sexual dysfunction, select the most likely clinical feature.

Accepted Answer

absence of orgasm with normal libido and erectile function

Answer

loss of sexual desire

Answer

failure of erection with absent nocturnal penile tumescence (NPT)

Answer

absence of emission

Question 8

What is the confirmatory test for Cushing's disease?

Accepted Answer

Bilateral inferior petrosal sinus sampling

Answer

High-dose dexamethasone suppression test

Answer

24-hour urine free cortisol

Answer

Overnight dexamethasone suppression test

Question 9

A 33-year-old man complains of a tingling sensation in his hands for several months, which occasionally awakens him during sleep. The patient has noticed he has gained weight and no longer wears his wedding ring as it has become too tight. Upon examination, the patient is noted to be sweating while speaking and has a prominent jaw, furrowed tongue, and large hands. His blood pressure is 142/91 mmHg. What is the most appropriate investigation?

Accepted Answer

Glucose tolerance test

Answer

MRI scan of the pituitary

Answer

Growth hormone levels

Answer

Serum prolactin levels

Question 10

A 45-year-old male with a known history of diabetes mellitus has an HbA1c of 9.4% despite strict glycemic control. Which of the following complications can be reversed?

Accepted Answer

None of the above

Answer

Retinopathy

Answer

Neuropathy

Answer

Nephropathy

Endocrinology — MCQs

Endocrinology — MCQs

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