**Question:** Normal glomerular filtration rate (GFR) in men is

A. 90
B. 60
C. 120
D. 144

**Correct Answer:** A. 90

**Core Concept:** Glomerular filtration rate (GFR) is a measure of the amount of urine produced in the kidneys. It is an important indicator of kidney function and is calculated using the formula:

GFR (ml/min) = (24-hour urine creatinine clearance × 100) / serum creatinine concentration

**Why the Correct Answer is Right:** The normal GFR in men is approximately 90 milliliters per minute (ml/min). This value is derived from the average 24-hour urine creatinine clearance, which is an estimation of the total amount of urine produced by the kidneys over 24 hours. A normal serum creatinine concentration is assumed for this calculation. A GFR of 90 ml/min indicates that the kidneys are functioning efficiently, filtering waste products and maintaining electrolyte and acid-base balance.

**Why Each Wrong Option is Incorrect:**

B. 60: This value is considered the lower limit of normal for GFR and is indicative of impaired kidney function. A GFR of 60 ml/min or less is considered stage 3 chronic kidney disease (CKD).

C. 120: This value is higher than the normal GFR and is not seen in healthy individuals. An elevated GFR indicates either increased filtration or reduced tubular reabsorption, leading to excessive urine production.

D. 144: This value is higher than the normal GFR and is not seen in healthy individuals. An elevated GFR indicates either increased filtration or reduced tubular reabsorption, leading to excessive urine production.

**Clinical Pearl:** The normal range of GFR varies based on the formula used and the reference values established in different populations. However, a GFR of 90 ml/min is considered the reference value for normal kidney function. Maintaining a normal GFR is essential for maintaining overall health, as the kidneys filter waste products, regulate electrolyte and acid-base balance, and produce erythropoietin, vitamin D, and other hormones. Impaired kidney function can lead to complications such as hypertension, anemia, and electrolyte imbalances.

**Why the Correct Answer is Right:** A normal GFR of 90 ml/min indicates efficient kidney function, which is crucial for maintaining homeostasis in the body. The kidneys filter waste products, regulate electrolyte and acid-base balance, and produce erythropoietin, vitamin D, and other hormones.

**Core Concept:** Glomerular filtration rate (GFR) is the gold standard for assessing kidney function. It is calculated based on the filtration fraction, which is calculated using serum creatinine concentration and the formula: GFR = (serum creatinine clearance × 100) / serum creatinine concentration. The normal GFR range is between 90-120 ml/min.

**Clinical Pearl:** A normal G