Final answer:
The true statement about glucose and the kidneys is that glucose starts to be excreted in the urine when the blood glucose level exceeds about 180 mg/dL, termed glycosuria. This is due to the renal threshold for glucose being surpassed, and it is especially prominent in uncontrolled diabetes mellitus where the glucose transporters' capacity is exceeded in the PCT.
Step-by-step explanation:
The statement B. Glucose begins to be lost in urine when the blood glucose level exceeds about 180 mg/dL is true regarding glucose and the kidneys. The kidneys have a renal threshold for glucose, which is approximately 180 mg/100 ml of blood. When blood glucose levels are below this threshold, glucose is efficiently reabsorbed from the filtrate in the proximal convoluted tubule (PCT), preventing it from being excreted in the urine.
However, if the blood glucose concentration exceeds this renal threshold, the capacity of glucose transporters is surpassed, resulting in glucose being excreted in the urine, a condition known as glycosuria. This is a common occurrence in uncontrolled diabetes mellitus, where high levels of glucose 'spill over' into the urine because the transport maximum (Tm) for glucose is exceeded.
In the case of choice D, in uncontrolled diabetes mellitus type I, the body does not retain glucose in the osmotic diuresis process; instead, glucose and large amounts of water are lost, leading to an increase in urine volume. Therefore, this statement is incorrect.