Which of the following is considered an abnormal constituent of urine in a healthy human being?

Introduction / Context:
The kidneys filter blood and form urine to remove metabolic wastes while conserving useful substances. Normal urine composition includes water, urea and certain other waste products, but some substances should be present only in very small amounts or not at all. Detecting abnormal constituents in urine is an important diagnostic tool. This question asks you to identify which listed substance is considered abnormal when found in significant quantity in the urine of a healthy person.

Given Data / Assumptions:

We are considering urine composition of a healthy individual. Options include creatinine, uric acid, glucose, urea and sodium ions. We assume normal kidney function without disease. We focus on substances whose presence at noticeable levels signals a problem.

Concept / Approach:
Normal urine contains water, urea, creatinine, uric acid, various ions (such as sodium, potassium and chloride) and small amounts of other dissolved substances. Glucose, however, is normally reabsorbed completely in the proximal tubule and should not appear in significant amounts in the urine. The presence of glucose in urine, known as glycosuria, often indicates uncontrolled diabetes mellitus or other conditions affecting renal glucose handling. Therefore, glucose is considered an abnormal constituent when found in measurable quantities in routine urine tests for healthy individuals.

Step-by-Step Solution:
Step 1: Recall the main nitrogenous wastes excreted in urine: urea, creatinine and uric acid. Step 2: Recognise that these wastes are normal final products of protein and nucleic acid metabolism. Step 3: Note that urine also normally contains various electrolytes such as sodium ions, depending on diet and body needs. Step 4: Remember that glucose is almost completely reabsorbed in the kidney tubules and does not usually appear in urine in healthy individuals. Step 5: Conclude that glucose, if present in measurable amounts, is an abnormal constituent indicating a possible disorder like diabetes.

Verification / Alternative check:
Urine analysis reports for healthy people list urea as the major nitrogenous waste and mention creatinine and uric acid as normal findings. Clinical textbooks emphasize that the renal threshold for glucose is such that blood glucose must rise above a certain level before any glucose spills into urine. Therefore, routine detection of glucose in urine is considered abnormal and prompts further testing for diabetes. By contrast, the presence of urea, creatinine, uric acid and sodium ions is expected, although their levels may vary.

Why Other Options Are Wrong:
Creatinine is a normal waste product formed from creatine in muscles and is regularly excreted by the kidneys. Uric acid is produced from the breakdown of purine nucleotides and also appears normally in urine. Urea is the main nitrogenous waste formed from ammonia in the liver and is the largest solid component of urine. Sodium ions are part of the body's normal electrolyte balance and are excreted in varying amounts depending on intake and kidney function. None of these are considered abnormal constituents when present within normal ranges.

Common Pitfalls:
Some students may think that any nitrogenous waste product is abnormal simply because it is a waste. However, normal urine is supposed to contain these waste materials. Others might focus on ions like sodium due to concerns about high salt intake, forgetting that sodium excretion is a normal function. The key to this question is recognising that glucose is a valuable energy source that the kidneys normally conserve. Its appearance in urine in significant amounts is a red flag rather than a usual finding.

Final Answer:
Among the given options, glucose is considered an abnormal constituent of urine in a healthy human being.