<prompt> Renal threshold for serum glucose level-100 mgdl200 mgdl300 mgdl400 mgdl  <response>: Ans. is b i.e., 200 mgdl The transport maximum for glucose is 375 mgmin whereas the filtered load of glucose is only 125 mgmin. Therefore, in normal conditions 100 of glucose is reabsorbed in proximal tubules. When plasma glucose concentration is 100 mgdl the filtered load is at its normal level, 125 mgmin, there is no loss of glucose in the urine. However, when the plasma concentration of glucose rises above about 200 mgdl, increasing the filtered load about 250 mgmin, a small amount of glucose begins to appear in the urine. This point is termed as threshold for glucose. Note that this appearance of glucose in the urine occurs before the transport maximum is reached. The reason for the difference between threshold and transport maximum is that not all nephron have same transport maimum for glucose, and some of the nephron therefore begin to excrete glucose before others have reached their transport maximum. The overall transport maximum for the kidneys, which is normally about 375 mgmin, is reached when all nephrons have reached their maximal capacity to reabsorb glucose. That means, above filtered load of 250 mgmin of glucose, some glucose will appear in the urine threshold level, whereas above filtered load of 375 mgmin, all the glucose will be excreted because all the nephrons have reached to their transport maximum. Thus, Renal threshold for glucosei At plasma levels - 200 mgdlii At filtered load - 250 mgmin 