Final answer:
In a healthy 5-year-old cat, glycosuria is most likely caused by diabetes mellitus, but could also be due to renal glycosuria, alimentary overconsumption of carbohydrates, or stress. Further diagnostic testing is required to pinpoint the exact cause.
Step-by-step explanation:
In a 5-year-old feline with glycosuria, the most likely cause could be an abnormality in the regulation of blood sugar levels. Diabetes mellitus is a common condition in cats where the cells are incapable of utilizing glucose effectively, leading to hyperglycemia and the resultant glycosuria due to the glucose exceeding the reabsorption capabilities of the kidneys. However, other potential causes such as Alimentary Glycosuria, Renal Glycosuria, and even stress-related Nervous Glycosuria should also be considered. It is important to investigate these potential causes with further diagnostic testing such as blood glucose levels, and consider the cat's health history and diet to determine the exact cause.
Conditions like renal glycosuria, where the renal threshold for glucose is lowered, sometimes due to drugs or inherited disorders, result in glucose being excreted in the urine despite normal or slightly elevated blood glucose levels. Other than diabetes mellitus, excessive carbohydrate intake or stress-related causes may lead to temporary episodes of glycosuria. Dietary factors should be evaluated, particularly if the condition is alimentary. Finally, polyuria—the excessive production of urine—may be observed, which can be caused by diabetes mellitus among other conditions.