Dear Neeraj, recall what all are majorly excreted in the tubular region of kidney??? K+ ion which is excreted is majorly to make the ionic balance of body. Also, Na+ and Cl- is also excreted depending upon the need. Together, all these maintains the ionic balance of the body that is , when in excess inside the body, the get away as tubular secretion. Similarly, H+ ions get secreted when more in number that is they maintain the pH of the body ( blood) by getting secreted out.