Endocrinology — MCQs

A 48-year-old Caucasian man, diagnosed with diabetes 5 years ago, presents with palpitations. Physical examination reveals diffuse skin darkening and testicular atrophy. Laboratory studies show elevated liver function and elevated blood sugars. A liver biopsy shows significantly elevated iron levels, leading to a diagnosis of hereditary hemochromatosis. Which one of the following laboratory findings is seen in hereditary hemochromatosis?

Q384Easy

Which of the following is responsible for fasting hypoglycemia?

Q385Medium

In patients with significant atherosclerosis, which of the following conditions is increased approximately 100-fold in those with comorbid diabetes compared to non-diabetic patients?

Q386Easy

Which of the following is true about primary aldosteronism?

Q387Easy

Which test can confirm autoimmune thyroiditis in a patient?

Q388Easy

A female patient has elevated TSH and subnormal free T4. What is the likely diagnosis?

Q389Easy

Testicular descent is controlled by which factor?

Q390Easy

All of the following are typically seen in Diabetic Ketoacidosis (DKA) except?

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 381: What is the imaging modality of choice for parathyroid pathology?

A. CT scan
B. Gallium scan
C. Thallium scan
D. Tc 99 scan (Correct Answer)

Explanation: **Explanation:** The imaging modality of choice for localizing parathyroid adenomas or hyperplasia is the **Technetium-99m (Tc-99m) Sestamibi scan**. This is a nuclear medicine study based on the principle that Sestamibi (a lipophilic cation) is taken up by mitochondria-rich cells. Parathyroid adenomas contain high concentrations of oxyphil cells with abundant mitochondria, which retain the tracer longer than the surrounding thyroid tissue. This "differential washout" allows for the identification of ectopic or enlarged parathyroid glands. **Analysis of Options:** * **A. CT scan:** While 4D-CT is increasingly used for surgical planning in re-operative cases, it is not the initial imaging of choice due to high radiation exposure and lower sensitivity compared to Sestamibi in primary cases. * **B. Gallium scan:** This is primarily used for detecting inflammation, infections, or certain lymphomas; it has no role in parathyroid imaging. * **C. Thallium scan:** Historically used in combination with Technetium (subtraction scanning), it has been largely replaced by Sestamibi due to the latter's superior image quality and sensitivity. * **D. Tc 99 scan (Correct):** Specifically, the **Tc-99m Sestamibi scan** (often combined with SPECT) is the gold standard for preoperative localization. **Clinical Pearls for NEET-PG:** * **First-line investigation:** Neck Ultrasound (USG) is often the initial step due to cost and availability, but **Sestamibi** is the most definitive for localization. * **Ectopic Parathyroid:** Sestamibi is particularly superior for identifying ectopic glands (e.g., in the mediastinum). * **Hungry Bone Syndrome:** A common post-operative complication of parathyroidectomy characterized by profound hypocalcemia and hypophosphatemia. * **Definitive Treatment:** Surgical excision (Parathyroidectomy) remains the only curative treatment for primary hyperparathyroidism.

Question 382: All of the following are associated with insulin resistance except?

A. Acanthosis nigricans
B. Lipodystrophy
C. Gout
D. Calcific aortic valve disease (Correct Answer)

Explanation: **Explanation:** Insulin resistance (IR) is a systemic metabolic state characterized by a decreased tissue response to insulin, leading to compensatory hyperinsulinemia. This condition is the hallmark of Metabolic Syndrome and is associated with specific cutaneous, metabolic, and cardiovascular manifestations. **Why Calcific Aortic Valve Disease (CAVD) is the correct answer:** While insulin resistance is a major risk factor for **atherosclerotic cardiovascular disease** (CAD), it is not a direct causative factor for **Calcific Aortic Valve Disease**. CAVD is primarily a degenerative process involving chronic inflammation, lipid accumulation, and osteoblast-like phenotypic changes in valve leaflets. While it shares risk factors with IR (like age and hypertension), it is not considered a classic clinical manifestation of the insulin resistance syndrome. **Analysis of other options:** * **Acanthosis Nigricans:** High insulin levels cross-react with **IGF-1 receptors** on keratinocytes and fibroblasts, leading to epidermal hyperplasia and the characteristic velvety, hyperpigmented plaques [1]. * **Lipodystrophy:** Both congenital and acquired lipodystrophies are strongly associated with severe insulin resistance due to the inability of adipose tissue to store triglycerides, leading to ectopic fat deposition in the liver and muscle [1]. * **Gout:** Hyperinsulinemia decreases the renal excretion of uric acid by upregulating the **URAT1 transporter** in the proximal tubule, leading to hyperuricemia and gout. **Clinical Pearls for NEET-PG:** * **PCOS** and **Nonalcoholic Fatty Liver Disease (NAFLD)** are also major clinical markers of insulin resistance. * **HAIR-AN Syndrome:** A high-yield triad consisting of **H**yper**a**ndrogenism, **I**nsulin **R**esistance, and **A**canthosis **N**igricans. * The most sensitive gold-standard test for measuring insulin resistance is the **Hyperinsulinemic Euglycemic Clamp study.**

Question 383: A 48-year-old Caucasian man, diagnosed with diabetes 5 years ago, presents with palpitations. Physical examination reveals diffuse skin darkening and testicular atrophy. Laboratory studies show elevated liver function and elevated blood sugars. A liver biopsy shows significantly elevated iron levels, leading to a diagnosis of hereditary hemochromatosis. Which one of the following laboratory findings is seen in hereditary hemochromatosis?

A. Decreased serum ceruloplasmin
B. Decreased serum ferritin
C. Decreased serum iron
D. Decreased total iron-binding capacity (Correct Answer)

Explanation: The clinical presentation of "Bronze Diabetes" (skin darkening and diabetes), testicular atrophy, and hepatomegaly in a middle-aged male is classic for **Hereditary Hemochromatosis (HH)** [2]. This is an autosomal recessive disorder (most commonly the HFE gene mutation) characterized by excessive intestinal iron absorption leading to systemic iron overload [1], [2]. **Why Option D is Correct:** In HH, the body is saturated with iron. **Total Iron-Binding Capacity (TIBC)** is an indirect measure of transferrin levels [4]. When iron stores are excessively high, the liver decreases the production of transferrin to prevent further transport of iron. Furthermore, since the existing transferrin molecules are highly saturated with iron (Transferrin Saturation >45-50%), the "capacity" to bind more iron is significantly **decreased**. **Why the Other Options are Incorrect:** * **Option A:** Decreased serum ceruloplasmin is the screening hallmark for **Wilson’s Disease** (copper overload), not hemochromatosis [3]. * **Option B:** Serum ferritin is an acute-phase reactant and a marker of total body iron stores. In HH, serum ferritin is **significantly elevated** (often >200-300 ng/mL) [1]. * **Option C:** Serum iron is **elevated** in HH due to increased absorption and release from damaged hepatocytes. **NEET-PG High-Yield Pearls:** * **Screening Test of Choice:** Transferrin Saturation (most sensitive early marker). * **Confirmatory Test:** Genetic testing for HFE mutation (C282Y) [1]. * **Gold Standard for Iron Quantification:** MRI (T2*) or Liver Biopsy (Perls' Prussian Blue stain) [1]. * **Classic Triad:** Cirrhosis, Diabetes Mellitus, and Skin Pigmentation [2]. * **Treatment:** Therapeutic phlebotomy is the mainstay; Deferoxamine is used if phlebotomy is contraindicated [1].

Question 384: Which of the following is responsible for fasting hypoglycemia?

A. Increased insulin level (Correct Answer)
B. Decreased insulin level
C. Increased glycogen
D. Increased glucagon in the liver

Explanation: Fasting hypoglycemia occurs when blood glucose levels drop below normal during periods of fasting (usually >4 hours after a meal). The physiological maintenance of blood glucose during fasting depends on a delicate balance between insulin (the primary anabolic hormone) and counter-regulatory hormones like glucagon, cortisol, and growth hormone [1]. **1. Why "Increased insulin level" is correct:** Insulin is the most potent hormone for lowering blood glucose. It suppresses hepatic gluconeogenesis and glycogenolysis (the two primary sources of glucose during fasting) and promotes glucose uptake in peripheral tissues like skeletal muscle and adipose tissue [2]. An absolute or relative excess of insulin—seen in conditions like an **Insulinoma** (a beta-cell tumor) or exogenous insulin administration—prevents the liver from releasing glucose, leading to profound fasting hypoglycemia [3]. **2. Why the other options are incorrect:** * **Decreased insulin level:** This is the normal physiological response to fasting. Low insulin levels allow for the activation of glycogenolysis and gluconeogenesis to maintain euglycemia [2]. * **Increased glycogen:** High stores of liver glycogen would actually protect against hypoglycemia by providing a ready source of glucose via glycogenolysis. * **Increased glucagon in the liver:** Glucagon is a counter-regulatory hormone. Increased glucagon levels stimulate the liver to produce glucose; therefore, it prevents rather than causes hypoglycemia [1]. **Clinical Pearls for NEET-PG:** * **Whipple’s Triad:** Essential for diagnosing hypoglycemia: (1) Symptoms of hypoglycemia, (2) Low plasma glucose, and (3) Relief of symptoms after glucose administration. * **Insulinoma vs. Factitious Insulin use:** In Insulinoma, both **Insulin and C-peptide** levels are elevated. In exogenous insulin injection, Insulin is high but **C-peptide is suppressed**. * **Non-pancreatic causes:** Always consider adrenal insufficiency (Addison’s disease) or severe liver disease in patients with fasting hypoglycemia.

Question 385: In patients with significant atherosclerosis, which of the following conditions is increased approximately 100-fold in those with comorbid diabetes compared to non-diabetic patients?

A. Myocardial infarction
B. Ischemic stroke
C. Lower limb ischemia (Correct Answer)
D. Vertebrobasilar insufficiency

Explanation: The correct answer is **Lower limb ischemia (Peripheral Arterial Disease)**. While diabetes mellitus (DM) is a major risk factor for all forms of macrovascular disease, the relative risk increase is most dramatic for lower extremity involvement [1]. In patients with atherosclerosis, the presence of diabetes increases the risk of gangrene and non-traumatic lower limb amputation by approximately **100-fold** compared to non-diabetics. This is due to a combination of accelerated atherosclerosis in the infra-popliteal (distal) vessels, peripheral neuropathy (leading to unnoticed trauma), and impaired wound healing. **Analysis of Incorrect Options:** * **A & B (Myocardial Infarction and Ischemic Stroke):** Diabetes is indeed a "coronary artery disease equivalent," increasing the risk of MI and stroke by 2 to 4 times. However, this increase is significantly lower than the 100-fold risk associated with limb-threatening ischemia. * **D (Vertebrobasilar insufficiency):** While DM contributes to cerebrovascular disease, it does not show the specific, massive statistical predilection for the vertebrobasilar system that it does for the distal lower limb arteries. **High-Yield Clinical Pearls for NEET-PG:** * **Pattern of Involvement:** Atherosclerosis in diabetics tends to be more **distal** (below the knee, involving tibial and peroneal arteries) and **multisegmental** compared to non-diabetics [1]. * **The "Rule of 100":** Remember that DM increases the risk of lower limb gangrene by ~100x. * **Monckeberg Medial Sclerosis:** Diabetics often have calcification of the arterial media, which can lead to falsely elevated Ankle-Brachial Index (ABI) readings. * **Leading Cause:** Diabetes is the leading cause of non-traumatic lower extremity amputations worldwide.

Question 386: Which of the following is true about primary aldosteronism?

A. Pedal edema
B. Increased renin
C. Increased Na+
D. Decreased K+ (Correct Answer)

Explanation: **Explanation:** Primary Aldosteronism (Conn’s Syndrome) is characterized by the autonomous overproduction of aldosterone from the adrenal cortex, independent of the renin-angiotensin system. **1. Why Decreased K+ is Correct:** Aldosterone acts on the principal cells of the renal collecting ducts to increase the reabsorption of sodium ($Na^+$) and the secretion of potassium ($K^+$) and hydrogen ions ($H^+$) [1]. Chronic excess of aldosterone leads to excessive urinary potassium loss, resulting in **hypokalemia**. This is a hallmark finding, often presenting clinically as muscle weakness or polyuria [1]. **2. Why the Other Options are Incorrect:** * **Pedal Edema:** Despite significant sodium and water retention, patients with primary aldosteronism typically **do not** have edema. This is due to the **"Aldosterone Escape"** phenomenon, where increased intravascular volume triggers the release of Atrial Natriuretic Peptide (ANP), causing pressure natriuresis and preventing fluid overload [2]. * **Increased Renin:** In primary aldosteronism, the high levels of aldosterone and subsequent volume expansion suppress the juxtaglomerular apparatus [3]. Therefore, **plasma renin activity (PRA) is low/suppressed**. A high Aldosterone-to-Renin Ratio (ARR) is the screening test of choice. * **Increased Na+:** While sodium is reabsorbed, the plasma sodium level usually remains in the **high-normal range** (hypernatremia is rare) because water is reabsorbed alongside sodium, and the "escape" mechanism limits total body sodium accumulation [2],[4]. **Clinical Pearls for NEET-PG:** * **Triad:** Hypertension, Hypokalemia, and Metabolic Alkalosis. * **Screening:** Plasma Aldosterone Concentration (PAC) to Plasma Renin Activity (PRA) ratio > 20-30. * **Confirmatory Test:** Saline infusion test or Oral salt loading test (failure to suppress aldosterone). * **Treatment:** Surgical excision for unilateral adenoma; Spironolactone (Aldosterone antagonist) for bilateral adrenal hyperplasia.

Question 387: Which test can confirm autoimmune thyroiditis in a patient?

A. Thyroid peroxidase antibody (TPO) (Correct Answer)
B. Antinuclear antibody
C. Thyroid uptake resin
D. Thyroid aspiration

Explanation: **Hashimoto’s thyroiditis (Chronic Autoimmune Thyroiditis)** is the most common cause of hypothyroidism in iodine-sufficient regions. The diagnosis is primarily clinical and biochemical, supported by the presence of specific autoantibodies. 1. **Why Option A is correct:** **Thyroid Peroxidase (TPO) antibodies** are the hallmark of autoimmune thyroiditis. They are present in more than **90-95%** of patients with Hashimoto’s. TPO is the enzyme responsible for iodine oxidation and organification; antibodies against it lead to thyroid follicle destruction [1]. While **Antithyroglobulin (anti-Tg)** antibodies can also be present, TPO antibodies are more sensitive and have a stronger correlation with the progression to overt hypothyroidism [1]. 2. **Why other options are incorrect:** * **B. Antinuclear antibody (ANA):** This is a screening test for systemic autoimmune diseases like SLE. While patients with Hashimoto’s may have co-existing autoimmune conditions, ANA is not specific to the thyroid. * **C. Thyroid uptake resin:** This (T3 resin uptake) is an older test used to estimate Thyroid Binding Globulin (TBG) levels. It does not identify the underlying autoimmune etiology. * **D. Thyroid aspiration (FNAC):** While FNAC can show characteristic Hurthle cells and lymphocytic infiltration, it is **not** the first-line confirmatory test. It is reserved for cases where a dominant nodule is present to rule out malignancy (e.g., Lymphoma or Papillary Carcinoma). **NEET-PG High-Yield Pearls:** * **Most sensitive marker:** Anti-TPO antibodies. * **Histology:** Lymphocytic infiltration with germinal centers and **Hurthle cells** (Askanazy cells/oxyphilic cells). * **Risk:** Increased risk of **B-cell Thyroid Lymphoma**. * **USG Finding:** Diffuse heterogenous echogenicity (often described as a "pseudonodular" appearance).

Question 388: A female patient has elevated TSH and subnormal free T4. What is the likely diagnosis?

A. Primary hypothyroidism (Correct Answer)
B. Secondary hypothyroidism
C. Hyperthyroidism
D. Subclinical hypothyroidism

Explanation: ### Explanation **1. Why Option A is Correct:** The diagnosis of **Primary Hypothyroidism** is based on the failure of the thyroid gland itself. When the thyroid gland cannot produce sufficient hormones (Low Free T4), the negative feedback mechanism to the pituitary is lost [1]. This results in the anterior pituitary secreting compensatory high levels of **Thyroid Stimulating Hormone (TSH)** to "force" the gland to work. Therefore, the classic biochemical profile is **↑ TSH and ↓ Free T4** [1]. **2. Why Other Options are Incorrect:** * **Secondary Hypothyroidism:** This occurs due to pituitary or hypothalamic failure. Since the "stimulator" is broken, the TSH will be **low or inappropriately normal** in the presence of a low Free T4. * **Hyperthyroidism:** This is characterized by an overactive gland. The biochemical profile shows **↓ TSH and ↑ Free T4/T3** [1]. * **Subclinical Hypothyroidism:** This is an early stage of thyroid failure where the TSH is **elevated**, but the thyroid gland is still able to maintain **normal Free T4** levels. **3. NEET-PG High-Yield Pearls:** * **Most Common Cause:** Worldwide, iodine deficiency is the most common cause; however, in iodine-sufficient areas (and the most common autoimmune cause), it is **Hashimoto’s Thyroiditis**. * **Screening Gold Standard:** Serum **TSH** is the most sensitive initial screening test for thyroid dysfunction [1]. * **Wolff-Chaikoff Effect:** Transient hypothyroidism caused by the ingestion of a large amount of iodine (e.g., amiodarone or contrast) [2]. * **Treatment Goal:** The target in primary hypothyroidism is to normalize TSH using Levothyroxine (T4), usually taken on an empty stomach [3].

Question 389: Testicular descent is controlled by which factor?

A. Insulin-like factor 3 (INSL3) (Correct Answer)
B. RANKL
C. FSH
D. LH

Explanation: Testicular descent is a complex, two-stage process. The correct answer is **Insulin-like factor 3 (INSL3)** because it is the primary hormone responsible for the first phase of descent. ### **Mechanism of Testicular Descent** 1. **Transabdominal Phase (Weeks 8–15):** This stage is controlled by **INSL3**, a peptide hormone secreted by the fetal Leydig cells. INSL3 acts on its receptor (RXFP2) to cause the thickening and contraction of the **gubernaculum**, which anchors the testes near the internal inguinal ring. 2. **Inguinoscrotal Phase (Weeks 25–35):** This stage is primarily **androgen-dependent** (Testosterone/DHT). Androgens cause the regression of the cranial suspensory ligament and guide the testes through the inguinal canal into the scrotum. ### **Analysis of Incorrect Options** * **RANKL (B):** This is a cytokine involved in bone metabolism (osteoclast activation). It has no role in gonadal development or descent. * **FSH (C):** Follicle-Stimulating Hormone is essential for spermatogenesis and Sertoli cell function but does not trigger the mechanical descent of the testes. * **LH (D):** While LH stimulates Leydig cells to produce testosterone (important for the second phase), **INSL3** is the specific factor required for the initial gubernacular development. ### **High-Yield Clinical Pearls for NEET-PG** * **Cryptorchidism:** Failure of descent is most commonly seen in preterm infants. The most common site of an undescended testis is the **inguinal canal**. * **Malignancy Risk:** Cryptorchidism increases the risk of testicular germ cell tumors (most commonly **Seminoma**), even if surgically corrected (Orchidopexy). * **Orchidopexy Timing:** Ideally performed between **6 to 12 months** of age to preserve fertility and allow for easier screening.

Question 390: All of the following are typically seen in Diabetic Ketoacidosis (DKA) except?

A. Tachycardia
B. Dehydration
C. Bradycardia (Correct Answer)
D. Abdominal pain/tenderness

Explanation: **Explanation:** Diabetic Ketoacidosis (DKA) is a life-threatening complication of Diabetes Mellitus characterized by the triad of hyperglycemia, ketosis, and metabolic acidosis [1]. **Why Bradycardia is the Correct Answer:** **Bradycardia** is not a typical feature of DKA. In fact, DKA patients almost always present with **Tachycardia** [1]. This occurs as a compensatory response to significant volume depletion (dehydration) and as a physiological reaction to metabolic stress and acidosis [1], [2]. If bradycardia is seen in a DKA patient, it is an ominous sign suggesting imminent cardiac arrest, severe hyperkalemia, or profound exhaustion. **Analysis of Incorrect Options:** * **Tachycardia:** As mentioned, this is a hallmark sign [1]. It is the body’s attempt to maintain cardiac output in the face of decreased intravascular volume (due to osmotic diuresis) [2]. * **Dehydration:** Hyperglycemia causes osmotic diuresis, leading to massive fluid loss [2]. Patients often have a fluid deficit of 5–10 liters, presenting with dry mucous membranes and decreased skin turgor [1]. * **Abdominal pain/tenderness:** This is a classic "pseudo-peritonitis" presentation in DKA, especially in children [1]. It is thought to be caused by delayed gastric emptying, ileus, or the metabolic acidosis itself. **NEET-PG High-Yield Pearls:** * **Kussmaul Respiration:** Deep, rapid breathing is a compensatory mechanism to blow off $CO_2$ and mitigate metabolic acidosis [1]. * **Potassium Paradox:** Total body potassium is always **depleted** in DKA (due to diuresis), but serum potassium may appear **normal or high** initially due to the extracellular shift of $K^+$ in exchange for $H^+$ ions [2]. * **Management Priority:** The first step in management is aggressive fluid resuscitation with Normal Saline (0.9% NaCl) [1]. * **Anion Gap:** DKA is a classic cause of High Anion Gap Metabolic Acidosis (HAGMA).

Practice by Chapter

Diabetes Mellitus

Practice Questions

Thyroid Disorders

Practice Questions

Adrenal Gland Disorders

Practice Questions

Pituitary Disorders

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Calcium and Bone Metabolism

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Reproductive Endocrinology

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Lipid Disorders

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Endocrine Hypertension

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Multiple Endocrine Neoplasia

Practice Questions

Obesity and Metabolic Syndrome

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Neuroendocrine Tumors

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Endocrine Emergencies

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