Final answer:
Diabetes mellitus is the condition likely to cause glucose levels to exceed the kidney's transport maximum, leading to glucosuria. This occurs when blood glucose exceeds about 180 mg/100 ml, overwhelming the GLUTs that reabsorb glucose in the proximal tubules.
Step-by-step explanation:
Among the conditions mentioned that might lead to glucose levels exceeding the transport maximum in the proximal tubules, diabetes mellitus is a direct cause. This is due to either insulin deficiency or defective insulin receptors. In this case, blood glucose levels can rise above the renal threshold, notably 180 mg/100 ml, causing the kidneys to excrete glucose through urine—a condition known as glucosuria. Diabetes insipidus, on the other hand, primarily affects water balance and does not typically lead to excess glucose in the urine.
The kidney's proximal tubules typically reabsorb almost 100 percent of the glucose filtered by the glomerulus. However, this reabsorption has a transport maximum (Tm). For men, it's about 375 mg/min, and for women, it's about 300 mg/min. When blood glucose levels exceed this Tm due to conditions like uncontrolled diabetes mellitus, glucose will appear in the urine as the carrier proteins, or glucose transport proteins (GLUTs), are overwhelmed.