Thiamine deficiency is best detected by estimating the activity of –
**Core Concept**
Thiamine, also known as Vitamin B1, is an essential nutrient that plays a crucial role in energy metabolism by facilitating the decarboxylation of alpha-keto acids in the Krebs cycle. A deficiency in thiamine can lead to impaired energy production in neurons and other cells, resulting in symptoms such as confusion, weakness, and peripheral neuropathy.
**Why the Correct Answer is Right**
The best indicator of thiamine deficiency is the activity of transketolase, an enzyme that participates in the pentose phosphate pathway and relies on thiamine pyrophosphate (TPP) as a cofactor. In the absence of thiamine, the activity of transketolase is significantly reduced, making it a reliable marker for thiamine deficiency. This is because transketolase is one of the most sensitive enzymes to thiamine deficiency, and its activity can be easily measured in erythrocytes or other tissues.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while lactate dehydrogenase (LDH) is an important enzyme in energy metabolism, its activity is not directly affected by thiamine deficiency.
**Option B:** This option is incorrect because while glucose-6-phosphate dehydrogenase (G6PD) is a key enzyme in the pentose phosphate pathway, its activity is not a direct indicator of thiamine deficiency.
**Option C:** This option is incorrect because while pyruvate kinase is an enzyme involved in glycolysis, its activity is not directly related to thiamine deficiency.
**Clinical Pearl / High-Yield Fact**
Thiamine deficiency is often seen in individuals with chronic alcoholism, malnutrition, or gastrointestinal disorders, and can be prevented or treated with thiamine supplements or injections.
**Correct Answer:** C. Transketolase