The metabolite excreted in urine in thiamine deficiency:

Appeared in: NVS- 2025

Explanation

Thiamine (Vitamin B1) in its active form, Thiamine Pyrophosphate (TPP), is a vital coenzyme for the Pyruvate Dehydrogenase (PDH) complex.
The PDH complex converts pyruvate, the final product of glycolysis, into acetyl-CoA, linking it to the Krebs cycle.
In thiamine deficiency, this conversion is blocked, leading to the accumulation of pyruvate in the blood.
The kidneys excrete this excess pyruvate, making it a key urinary marker for thiamine deficiency.

Option A: Xanthurenic acid (a type of xanthinic acid) is a marker for Vitamin B6 (pyridoxine) deficiency, not thiamine deficiency. It accumulates due to altered tryptophan metabolism.
Option B: FIGLU (Formiminoglutamic acid) is excreted in the urine during Folic acid (Vitamin B9) deficiency, as folate is required for its metabolism.
Option D: Glucose in the urine (glycosuria) is characteristic of conditions with high blood sugar, primarily uncontrolled Diabetes Mellitus, not a specific vitamin deficiency.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Biochemical markers of vitamin deficiencies as background academic context rather than a clinical decision trigger.
Nurses should be aware that patients with chronic alcoholism, malnutrition, or those on long-term diuretic therapy are at high risk for thiamine deficiency.
The clinical manifestations, such as Wernicke-Korsakoff syndrome (confusion, ataxia, ophthalmoplegia) or Beriberi (neuropathy, heart failure), are serious. Early recognition and testing, which can include checking for pyruvate levels, is crucial.
What if? If a patient with a history of alcoholism presents with confusion and ataxia, the nurse should anticipate orders for intravenous thiamine administration before giving any glucose-containing fluids. Giving glucose first can worsen the deficiency and precipitate Wernicke's encephalopathy.

How to Approach the Question

First, identify the core concept of the question, which is the biochemical consequence of 'thiamine deficiency'.
Recall the primary metabolic role of thiamine (Vitamin B1). It is a key coenzyme in carbohydrate metabolism.
Connect this role to the options provided. Thiamine is essential for the enzyme that processes pyruvate.
Therefore, a deficiency will cause the substance acted upon by that enzyme (pyruvate) to build up.
Evaluate the other options to confirm your answer. Recall or deduce that Xanthurenic acid, FIGLU, and Glucose are markers for different conditions (B6 deficiency, folate deficiency, and diabetes, respectively).

Concept Tested & Keywords

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E6 Harper's Illustrated Biochemistry2023 (pp 26-793 of 813) p. 284-286

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 1 (pp 26-370 of 370) p. 315-317

Practise the full NVS- 2025

Attempt every question from this paper in a timed mock, then review the full solution for each one.