Endocrinology Practice Questions

Q: What fasting blood glucose level is indicative of diabetes mellitus?

126 mg/dl. **Explanation:** The diagnosis of Diabetes Mellitus (DM) is based on specific glycemic thresholds defined by the American Diabetes Association (ADA). **1. Why Option A is correct:** According to current diagnostic criteria, a **Fasting Plasma Glucose (FPG) level ≥ 126 mg/dl (7.0 mmol/L)** is indicative of Diabetes Mellitus [1]. "Fasting" is defined as no caloric intake for at least 8 hours. This threshold is chosen because it correlates with a significantly increased risk of developing microvascular complications, particularly diabetic retinopathy [1]. **2. Analysis of Incorrect Options:** * **Option B (140 mg/dl):** While this value is diagnostic of diabetes (as it is >126 mg/dl), it is not the *minimum* threshold. Additionally, 140 mg/dl is the cutoff for the 2-hour post-load glucose in **Impaired Glucose Tolerance (IGT)**. * **Option C (100 mg/dl):** This is the upper limit of normal. An FPG between **100–125 mg/dl** is categorized as **Impaired Fasting Glucose (IFG)**, a state of pre-diabetes [1]. * **Option D (200 mg/dl):** This is the diagnostic threshold for a **Random Plasma Glucose** (in a symptomatic patient) or a **2-hour Plasma Glucose** during an Oral Glucose Tolerance Test (OGTT). **High-Yield Clinical Pearls for NEET-PG:** * **HbA1c Criteria:** A level of **≥ 6.5%** is diagnostic for DM; **5.7–6.4%** indicates pre-diabetes. * **Confirmatory Testing:** Unless there is clear clinical hyperglycemia (polyuria, polydipsia, weight loss) with a random glucose ≥ 200 mg/dl, the diagnosis requires **two abnormal test results** from the same sample or two separate test samples. * **Gold Standard:** The OGTT is considered the most sensitive test for diagnosis, though FPG and HbA1c are more commonly used in clinical practice.

Q: Dilutional hyponatremia is seen in which of the following conditions or agents?

Vincristine. **Explanation** The correct answer is **Vincristine**. **1. Why Vincristine is Correct:** Vincristine (a vinca alkaloid used in chemotherapy) is a well-known cause of **SIADH (Syndrome of Inappropriate Antidiuretic Hormone secretion)**. It exerts a neurotoxic effect on the hypothalamus and posterior pituitary, leading to the excessive release of ADH. High levels of ADH cause water reabsorption in the renal collecting ducts [1], leading to water retention and **dilutional hyponatremia** (euvolemic hyponatremia) [2]. **2. Analysis of Incorrect Options:** * **Addison’s Disease:** This causes **hypovolemic hyponatremia**. The deficiency of aldosterone leads to "salt wasting" (loss of sodium and water), but the sodium loss exceeds water loss [2]. * **Diuretic Therapy:** Thiazides and loop diuretics cause hyponatremia primarily through the depletion of total body sodium and water (**hypovolemic hyponatremia**) [2], not through primary water retention. * **Craniopharyngioma:** This tumor typically destroys the posterior pituitary or hypothalamus, leading to a *deficiency* of ADH, resulting in **Diabetes Insipidus** (hypernatremia due to excessive water loss), rather than hyponatremia [3]. **3. NEET-PG High-Yield Pearls:** * **Drugs causing SIADH:** Remember the mnemonic **"S-C-V-C"**: **S**SRIs, **C**yclophosphamide/Carbamazepine, **V**incristine/Vinblastine, **C**hlorpropamide. * **Diagnostic Criteria for SIADH:** Euvolemic status [2], low serum osmolality ( 100 mOsm/kg). * **Management:** The first-line treatment for SIADH is **fluid restriction**. For severe symptomatic cases, hypertonic saline (3%) is used, but must be administered carefully to avoid Central Pontine Myelinolysis.

Q: A 48-year-old woman presents with complaints of moderate weight loss over the past 6 months, heat intolerance, palpitations, and fine tremors in the hands. Physical examination reveals the presence of a diffuse goiter and exophthalmos. Which of the following laboratory findings would be expected in this individual?

Increased plasma concentration of thyroglobulin. The clinical presentation of weight loss, heat intolerance, tremors, diffuse goiter, and **exophthalmos** is pathognomonic for **Graves' Disease** (hyperthyroidism) [1], [3]. **Why Option D is Correct:** Thyroglobulin (Tg) is a large glycoprotein synthesized by follicular cells and stored within the thyroid colloid. In Graves' Disease, the thyroid gland is hyperactive due to stimulation by Thyroid Stimulating Immunoglobulins (TSI) [3]. This hyperfunction, along with increased glandular vascularity and follicular cell turnover, leads to an **increased leakage of thyroglobulin into the plasma**. Therefore, plasma Tg levels are elevated in almost all forms of hyperthyroidism (except factitious thyrotoxicosis) [2]. **Analysis of Incorrect Options:** * **A. Decreased serum T4:** In hyperthyroidism, serum T4 (and T3) levels are characteristically **increased** due to overproduction by the thyroid gland [1]. * **B. Decreased radioactive iodine uptake (RAIU):** Graves' Disease is characterized by **increased (diffuse) RAIU** because the gland is actively synthesizing thyroid hormones [2]. Decreased uptake is seen in thyroiditis or factitious ingestion [2]. * **C. Decreased resin T3 uptake:** Resin T3 uptake measures the saturation of Thyroid Binding Globulin (TBG). In hyperthyroidism, high levels of endogenous T4 saturate the TBG binding sites, leaving fewer sites available for the resin test. This results in an **increased resin T3 uptake**. **NEET-PG High-Yield Pearls:** * **Graves' Disease Triad:** Hyperthyroidism + Diffuse Goiter + Exophthalmos (Ophthalmopathy) +/- Pretibial Myxedema [3]. * **Thyroglobulin (Tg) Marker:** It is a crucial marker to differentiate **Factitious Thyrotoxicosis** (low Tg due to exogenous hormone suppressing the gland) from **Graves' or Thyroiditis** (high Tg) [2]. * **Antibody:** The most specific antibody for Graves' is **TSH-receptor antibody (TRAb/TSI)** [3].

Q: What is the most common paroxysmal symptom of pheochromocytoma?

Headache. Explanation: Pheochromocytoma is a catecholamine-secreting tumor arising from chromaffin cells of the adrenal medulla. The classic presentation involves paroxysmal episodes (spells) caused by the sudden release of epinephrine and norepinephrine. Why Headache is Correct: Headache is the most common symptom during a paroxysmal attack, occurring in up to 90% of symptomatic patients. It is typically sudden in onset, severe, and throbbing in nature, resulting from acute hypertensive surges and cerebral vasodilation. Analysis of Incorrect Options: * B. Palpitations: While very common (occurring in ~50-70% of cases), palpitations are statistically less frequent than headaches. The classic triad of pheochromocytoma consists of Headache, Perspiration (Diaphoresis), and Palpitations. * C. Abdominal pain: This is a less common symptom, usually occurring due to mesenteric vasoconstriction or associated complications like intestinal ischemia, but it is not a hallmark paroxysmal feature. * D. Hypotension: Pheochromocytoma typically causes hypertension (either sustained or paroxysmal). Orthostatic hypotension can occur due to low plasma volume, but it is not a primary paroxysmal symptom. NEET-PG High-Yield Pearls: * The Rule of 10s: 10% bilateral, 10% malignant, 10% pediatric, 10% extra-adrenal (Paragangliomas), and 10% familial. * Diagnosis: The most sensitive initial screening test is 24-hour urinary fractionated metanephrines or plasma free metanephrines. * Management: Always start Alpha-blockade (e.g., Phenoxybenzamine) before Beta-blockade to avoid an unopposed alpha-mediated hypertensive crisis. * Genetic Associations: MEN 2A, MEN 2B, von Hippel-Lindau (VHL) syndrome, and Neurofibromatosis type 1 (NF1).

Q: Which laboratory test is the investigation of choice for confirming myxedema coma?

Thyroid stimulating hormone (TSH). **Explanation:** **Myxedema coma** is a life-threatening complication of severe, long-standing hypothyroidism. The diagnosis is primarily **clinical**, based on the triad of altered mental status, hypothermia, and a precipitating event. However, laboratory confirmation is essential. 1. **Why TSH is the Investigation of Choice (Option A):** In the vast majority of cases (>95%), myxedema coma results from primary thyroid failure. **Serum TSH** is the most sensitive and reliable marker to confirm primary hypothyroidism [1]. It will be significantly elevated in primary cases. While a low Free T4 is also present, the TSH level is the definitive test to establish the etiology and confirm the diagnosis in the context of clinical symptoms. 2. **Why other options are incorrect:** * **TRH (Option B):** TRH stimulation tests are obsolete in acute settings and are not used to diagnose myxedema coma [1]. * **T3 (Option C):** Serum T3 levels are often the last to fall and can be low in non-thyroidal illness (Sick Euthyroid Syndrome); therefore, T3 is unreliable for diagnosing hypothyroidism [2]. * **T4 (Option D):** While Free T4 will be low in myxedema coma, it cannot differentiate between primary and secondary (central) causes without a concurrent TSH [2]. TSH remains the primary screening and confirmatory tool. **NEET-PG High-Yield Pearls:** * **Treatment Priority:** Do NOT wait for lab results to start treatment if clinical suspicion is high. * **Management:** The treatment of choice is **IV Levothyroxine (T4)**, often supplemented with **IV Liothyronine (T3)**. * **Steroid Rule:** Always administer **IV Hydrocortisone** before thyroid hormone replacement to prevent an adrenal crisis (as the patient may have co-existing adrenal insufficiency). * **Commonest Precipitant:** Infection (e.g., pneumonia, UTI) or discontinuation of thyroid medication.

Question 1

What fasting blood glucose level is indicative of diabetes mellitus?

Accepted Answer

126 mg/dl

Answer

140 mg/dl

Answer

100 mg/dl

Answer

200 mg/dl

Question 2

What is the immediate treatment of hypercalcemia of malignancy?

Accepted Answer

IV fluids

Answer

Bisphosphonates

Answer

Calcitonin

Answer

Glucocorticoids

Question 3

Dilutional hyponatremia is seen in which of the following conditions or agents?

Accepted Answer

Vincristine

Answer

Addison's disease

Answer

Diuretic therapy

Answer

Craniphyrangioma

Question 4

A 48-year-old woman presents with complaints of moderate weight loss over the past 6 months, heat intolerance, palpitations, and fine tremors in the hands. Physical examination reveals the presence of a diffuse goiter and exophthalmos. Which of the following laboratory findings would be expected in this individual?

Accepted Answer

Increased plasma concentration of thyroglobulin

Answer

Decreased serum T4

Answer

Decreased radioactive iodine uptake

Answer

Decreased resin T3 uptake

Question 5

A 65-year-old male patient complains of loss of libido and is found to have low free and total testosterone levels. Treatment is commenced with testosterone supplemental therapy. What is the next step in management after testosterone administration?

Accepted Answer

Check PSA levels

Answer

Testosterone levels are decreased

Answer

Decrease in size of benign prostatic tissue lesions occurs

Answer

Decrease in size of prostatic cancer occurs

Question 6

What is the most common paroxysmal symptom of pheochromocytoma?

Accepted Answer

Headache

Answer

Palpitations

Answer

Abdominal pain

Answer

Hypotension

Question 7

Which laboratory test is the investigation of choice for confirming myxedema coma?

Accepted Answer

Thyroid stimulating hormone (TSH)

Answer

Thyrotropin releasing hormone (TRH)

Answer

Triiodothyronine (T3)

Answer

Tetraiodothyronine (T4)

Question 8

A 30-year-old male presents with fatigue, muscle weakness, headache, hypertension (170/120 mm Hg), and tachycardia (100/min). Laboratory findings include hypokalemia, metabolic alkalosis, and decreased plasma renin activity. A CT scan reveals a mass on the left suprarenal gland. After a few weeks of treatment with a specific medication, his symptoms resolved, and laboratory values and blood pressure normalized. What is the likely medication prescribed?

Accepted Answer

Spironolactone

Answer

Clonidine

Answer

Propranolol

Answer

Hydrochlorothiazide

Question 9

In a patient experiencing thyroid crisis, characterized by hyperpyrexia, tachycardia, vomiting, dehydration, and shock, which of the following interventions is usually indicated?

Accepted Answer

Propranolol

Answer

Metaraminol

Answer

Glucocorticoids

Answer

Intravenous saline

Question 10

A patient presents with intermittent headache. On examination, there is hypertension and a thyroid nodule. Which of the following steps is to be taken next?

Accepted Answer

Urine VMA and aspiration of the thyroid nodule

Answer

Urine HIAA levels

Answer

Ultrasound abdomen

Answer

Echocardiography

Endocrinology — MCQs

Endocrinology — MCQs

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