Question

Hi,

How does hyperglycemia result in osmotic diuresis?

Can I have a step-by-step process. Thank you!

Answer 1

Hyperglycemia occurs because of insulin deficiency or glucagon exceas. Insulin is a major anabolic hormone. Its deficiency results in a catabolic state, that affects not only glucose metabolism but also fat and protein metabolism. Unopposed secretion of counterregulatory hormones (glucagon, epinephrine, growth hormone) also plays a role in these metabolic derangements. The assimilation of glucose into muscle and adipose tissue is sharply diminished. Not only does a storage of glycogen in liver and muscle cease, but also reserves are depleted by glycogenolysis. Resultant hyperglycemia exceeds the renal threshold for your absorption. {Renal threshold is the plasma glucose concentration at which glucose first appears in the urine. Its normal value is 120 to 200 mg/dL. At plasma levels below renal threshold, all of the filtered glucose can be reabsorbed because plenty of carriers are available and hence no glucose is excreted in urine.} As the renal threshold for glucose is exceeded, the carriers become saturated and no more carrier is available for glucose to bind to. Therefore glucose starts appearing in the urine (glycosuria). The Glucose is an osmotically active molecule. Whenever there is Glucose, it will attract water to it. Hence glycosuria induces an osmotic diuresis.