Examination revealed that the patient is hyperglycemic high

Examination revealed that the patient is hyperglycemic (high blood glucose). How do chronically high blood glucose levels correlate with increased urine output and thirst? How does it affect the osmotic gradient along the loop of Henle?

Solution

In a normal person, whatever the quantity of glucose that enters Bowman’s capsule and proximal convoluted tubule, all the glucose is reabsorbed into body from PCT and the urine would contain no glucose.

Whereas, in hyperglycemic persons, higher quantity of glucose enters the Bowman’s capsule and PCT. This level of glucose exceeds the maximum reabsorption capacity of PCT so that glucose still remains in the nephron i.e, during its movement from loop of henle, distal convoluted tubule and collecting ducts. Since, the urine is also hyperglycemic, glucose draws more water into urine by osmosis. Thus in a diabetic, hyperglycemia causes to produce a high volume of glucose containing urine.

The urine in loop of henle would be hyperosmotic.