Trace Elements and Metabolism — MCQs
Which of the following trace elements has vitamin E-like action?
A dental surgeon appointed in a rural health centre reports an increased incidence of dental caries in the people of that area. Research team confirmed that water supply of that area is deficient in
Menkes disease is caused by a deficiency of which protein?
Deficiency of which element is specifically linked to the syndrome of growth failure, anemia, and hypogonadism?
Selenium deficiency is seen in -
All are increased in IDA except
Wolf Chaikoff effect:
Which of the following statements about Wilson's disease is true?
Deficiency of which of the following micronutrients results in Menkes syndrome?
Which of the following conditions is associated with hypokalemia and metabolic acidosis?
Trace Elements and Metabolism Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following trace elements has vitamin E-like action?
- A. Iron
- B. Selenium (Correct Answer)
- C. Copper
- D. Zinc
Explanation: ***Selenium*** - Selenium is an essential component of **glutathione peroxidase**, an enzyme that works alongside vitamin E to protect cells from **oxidative damage**. - Its antioxidant properties are similar to **vitamin E**, as both scavenge free radicals and prevent lipid peroxidation. *Iron* - Iron is vital for **oxygen transport** in hemoglobin and myoglobin, and for cellular respiration as a component of cytochromes. - While essential, iron does not have direct **antioxidant properties** akin to vitamin E; in excess, it can even promote oxidative stress. *Copper* - Copper is a cofactor for several enzymes, including **superoxide dismutase (SOD)**, an antioxidant enzyme, but its primary role is not directly analogous to vitamin E's lipid-soluble antioxidant function. - It also plays a role in **energy production**, iron metabolism, and neurotransmission. *Zinc* - Zinc is crucial for **immune function**, wound healing, and DNA synthesis, acting as a cofactor for over 300 enzymes. - Although it has indirect antioxidant effects by stabilizing cell membranes and reducing oxidative damage, its mechanism and direct action are not considered "vitamin E-like."
Question 2: A dental surgeon appointed in a rural health centre reports an increased incidence of dental caries in the people of that area. Research team confirmed that water supply of that area is deficient in
- A. Chloride
- B. Sodium
- C. Fluoride (Correct Answer)
- D. Calcium
Explanation: ***Fluoride*** - **Fluoride** strengthens tooth enamel, making it more resistant to acid attacks from bacteria and thus preventing **dental caries**. - A deficiency in the water supply would directly lead to decreased fluoride exposure, increasing the incidence of **tooth decay**. *Chloride* - **Chloride** is an essential electrolyte involved in fluid balance and nerve function, but it has no direct role in preventing **dental caries**. - Its presence or absence in drinking water does not significantly impact tooth decay rates. *Sodium* - **Sodium** is another essential electrolyte vital for nerve and muscle function, but it does not contribute to the prevention of **dental caries**. - Its levels in water are unrelated to tooth enamel strength or susceptibility to decay. *Calcium* - While **calcium** is a major component of tooth structure, its primary role in dental health is during tooth development and in maintaining bone density. - Deficiency in water supply is not typically linked to increased **dental caries** risk in the same way as fluoride deficiency, as systemic calcium intake is more critical.
Question 3: Menkes disease is caused by a deficiency of which protein?
- A. ATP7B (Wilson disease protein)
- B. Ceruloplasmin
- C. Copper-zinc superoxide dismutase
- D. ATP7A (copper-transporting ATPase) (Correct Answer)
Explanation: ***ATP7A (copper-transporting ATPase)*** - **Menkes disease** is an X-linked recessive disorder caused by a mutation in the **ATP7A gene**, which encodes a copper-transporting ATPase. - This protein is essential for **copper absorption** from the intestines and its transport across cell membranes. *ATP7B (Wilson disease protein)* - Mutations in the **ATP7B gene** cause **Wilson disease**, characterized by **copper accumulation** in the liver, brain, and other organs due to impaired copper excretion. - Unlike Menkes disease, Wilson disease involves *too much* copper in tissues, not a deficiency due to poor absorption. *Ceruloplasmin* - **Ceruloplasmin** is a copper-carrying protein that transports copper in the blood and also acts as an oxidase. - While deficiencies in ceruloplasmin can lead to **aceruloplasminemia**, a disorder of iron metabolism, it is not the primary defect in Menkes disease. *Copper-zinc superoxide dismutase* - **Copper-zinc superoxide dismutase (SOD1)** is an enzyme that plays a crucial role in eliminating harmful **reactive oxygen species**. - Mutations in SOD1 are associated with some forms of **amyotrophic lateral sclerosis (ALS)**, not Menkes disease.
Question 4: Deficiency of which element is specifically linked to the syndrome of growth failure, anemia, and hypogonadism?
- A. Calcium
- B. Copper
- C. Zinc (Correct Answer)
- D. Magnesium
Explanation: ***Zinc*** - **Zinc deficiency** is classically associated with **growth retardation**, **anemia**, **hypogonadism**, and impaired immune function due to its role in numerous enzymatic processes and DNA synthesis. - It plays a crucial role in **cellular growth**, development, and endocrine function, making its deficiency particularly impactful on these systems. *Calcium* - **Calcium deficiency** primarily leads to **bone demineralization** (osteoporosis or osteomalacia), tetany, and muscle cramps. - While essential for growth, it is not specifically linked to the triad of **anemia** and **hypogonadism** in the same manner as zinc. *Copper* - **Copper deficiency** can cause **anemia** (microcytic, unresponsive to iron), **neurological dysfunction** (myelopathy), and impaired immune function. - However, it is not typically associated with prominent **growth failure** and **hypogonadism** as a primary triad of symptoms. *Magnesium* - **Magnesium deficiency** can lead to **neuromuscular hyperexcitability** (tetany, spasms), cardiac arrhythmias, and fatigue. - It does not commonly present with the distinct combination of **growth failure**, **anemia**, and **hypogonadism**.
Question 5: Selenium deficiency is seen in -
- A. Keshan disease (Correct Answer)
- B. Wilson disease
- C. Acrodermatitis enteropathica
- D. None of the options
Explanation: ***Keshan disease*** - **Keshan disease** is a form of **cardiomyopathy** caused by **selenium deficiency**, particularly prevalent in regions with selenium-poor soil. - It presents with **heart failure**, arrhythmias, and cardiac enlargement. *Wilson disease* - **Wilson disease** is a disorder of **copper metabolism**, leading to excessive copper accumulation in organs, primarily the liver and brain. - It is not related to selenium deficiency. *Acrodermatitis enteropathica* - **Acrodermatitis enteropathica** is a genetic disorder of **zinc deficiency**, characterized by dermatitis, diarrhea, and alopecia. - It does not involve selenium deficiency. *None of the options* - This option is incorrect because Keshan disease is directly linked to selenium deficiency.
Question 6: All are increased in IDA except
- A. Transferrin saturation (Correct Answer)
- B. TIBC
- C. Soluble transferrin receptor
- D. Erythropoietin
Explanation: ***Transferrin saturation*** - In **iron deficiency anemia (IDA)**, there is insufficient iron to saturate transferrin, leading to a **decreased** transferrin saturation. This is the exception among the given options. - Transferrin saturation is calculated as (serum iron / TIBC) x 100, and both **serum iron** and its percentage saturation are low in IDA. *TIBC* - **Total iron-binding capacity (TIBC)** is typically **increased** in IDA as the liver produces more transferrin in an attempt to capture more iron [1]. - This elevated TIBC reflects the body's compensatory mechanism to maximize available iron uptake. *Soluble transferrin receptor* - **Soluble transferrin receptor (sTfR)** levels are **elevated** in IDA because iron-deficient erythroblasts upregulate the production of transferrin receptors on their surface as they try to scavenge more iron. - The elevated sTfR is a sensitive and specific marker for **iron deficiency**, particularly useful in differentiating IDA from anemia of chronic disease [1]. *Erythropoietin* - **Erythropoietin (EPO)** levels are **increased** in IDA due to the kidney's response to the decreased oxygen-carrying capacity of the blood (anemia) [1]. - EPO stimulates the bone marrow to produce more red blood cells, which exacerbates the demand for iron, often leading to further iron depletion if iron stores are low.
Question 7: Wolf Chaikoff effect:
- A. Iodine induced hyperthyroidism
- B. Drug induced hyperthyroidism
- C. Iodine induced hypothyroidism (Correct Answer)
- D. Thyrotoxicosis due to excessive amount of thyroid hormone ingestion
Explanation: ***Iodine induced hypothyroidism*** - The **Wolf-Chaikoff effect** describes the phenomenon where a high concentration of **iodide** temporarily inhibits the synthesis and release of thyroid hormones. - This transient effect leads to a short period of **hypothyroidism** in response to excess iodine. *Iodine induced hyperthyroidism* - This describes **Jod-Basedow phenomenon**, which is distinct from the Wolf-Chaikoff effect. - **Jod-Basedow** occurs when iodine administration in an iodine-deficient individual or someone with pre-existing thyroid abnormalities leads to **hyperthyroidism**. *Drug induced hyperthyroidism* - This is a broad category referring to hyperthyroidism caused by various medications, such as **amiodarone**, but does not specifically define the Wolf-Chaikoff effect. - The Wolf-Chaikoff effect specifically relates to the direct inhibitory action of high **iodine** concentrations on the thyroid gland. *Thyrotoxicosis due to excessive amount of thyroid hormone ingestion* - This condition is known as **thyrotoxicosis factitia** or **exogenous thyrotoxicosis**. - It is distinct from the Wolf-Chaikoff effect, which involves the thyroid gland's self-regulatory response to **iodine** overload rather than external hormone intake.
Question 8: Which of the following statements about Wilson's disease is true?
- A. Low serum ceruloplasmin and low urinary copper
- B. Low serum ceruloplasmin and high urinary copper (Correct Answer)
- C. High serum ceruloplasmin and low urinary copper
- D. High serum ceruloplasmin and high urinary copper
Explanation: ***Low serum ceruloplasmin and high urinary copper*** - In **Wilson's disease**, there is a defect in **copper transport**, leading to impaired incorporation of copper into ceruloplasmin and reduced biliary excretion. - This results in **low serum ceruloplasmin** levels (since ceruloplasmin is the main copper-carrying protein in the blood) and **increased urinary copper excretion** as the body attempts to eliminate excess free copper. *Low serum ceruloplasmin and low urinary copper* - While **low serum ceruloplasmin** is characteristic, **low urinary copper** would indicate adequate copper elimination or a different condition, which is not the case for Wilson's disease. - Patients with Wilson's disease have **excess copper accumulation**, and increased urinary excretion is a compensatory mechanism [1]. *High serum ceruloplasmin and low urinary copper* - **High serum ceruloplasmin** is inconsistent with Wilson's disease, as ceruloplasmin levels are typically low due to the impaired copper binding. - **Low urinary copper** excretion would indicate normal or low total body copper, which contradicts the copper overload seen in Wilson's disease. *High serum ceruloplasmin and high urinary copper* - **High serum ceruloplasmin** would suggest normal or increased ceruloplasmin synthesis or release, which is contrary to the pathophysiology of Wilson's disease. - Although **high urinary copper** is a feature, it isn't accompanied by high ceruloplasmin in this condition, as ceruloplasmin is primarily involved in carrying copper in the blood rather than excreting excess copper [1].
Question 9: Deficiency of which of the following micronutrients results in Menkes syndrome?
- A. Magnesium
- B. Copper (Correct Answer)
- C. Selenium
- D. Manganese
Explanation: **Copper** - **Menkes syndrome** is a genetic disorder caused by a defect in the **ATP7A gene**, leading to impaired cellular copper transport and severe **copper deficiency**. - This deficiency affects multiple organ systems, resulting in characteristic features like **kinky hair**, **neurological degeneration**, and connective tissue abnormalities. *Magnesium* - Magnesium deficiency is associated with conditions like **hypomagnesemia**, muscle weakness, and cardiac arrhythmias. - It plays crucial roles in enzyme function and nerve conduction but is not directly linked to Menkes syndrome. *Selenium* - Selenium deficiency can cause **Keshan disease** (cardiomyopathy) and **myxedematous endemic cretinism**. - While an essential trace element, its deficiency does not lead to Menkes syndrome. *Manganese* - Manganese is a cofactor for several enzymes involved in metabolism and antioxidant defense. - Deficiency is rare and typically presents with impaired growth and bone development, which are distinct from Menkes syndrome.
Question 10: Which of the following conditions is associated with hypokalemia and metabolic acidosis?
- A. Diarrhea (Correct Answer)
- B. Vomiting
- C. Nasogastric suction
- D. Renal tubular acidosis
Explanation: ***Diarrhea*** - Severe **diarrhea** leads to the loss of **bicarbonate-rich fluids** from the gastrointestinal tract, causing **metabolic acidosis**. [1] - It also results in significant **potassium loss**, leading to **hypokalemia**. [1] *Vomiting* - **Vomiting** typically causes the loss of **acidic gastric contents**, leading to **metabolic alkalosis**, not acidosis. [1], [2] - While it can cause **hypokalemia** due to fluid loss and renal compensation, the primary acid-base disturbance is alkalosis. [1] *Nasogastric suction* - Similar to vomiting, **nasogastric suction** removes **hydrochloric acid** from the stomach, primarily causing **metabolic alkalosis**. [1] - Hypokalemia can occur due to the loss of potassium and renal compensation for alkalosis, but acidosis is not the primary feature. *Renal tubular acidosis* - **Renal tubular acidosis (RTA)** is characterized by the **kidneys' inability to excrete acid** or **reabsorb bicarbonate**, leading to **metabolic acidosis**. [2] - While some forms of RTA (e.g., type 1 and type 2) are associated with **hypokalemia**, not all forms cause hypokalemia, and the primary issue is renal acid-base dysfunction. [2]
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