Excessive protein consumption is not only the chief cause of osteoporosis, there are other problems that are also derived from too much protein, particularly too much animal protein. One such problem is kidney stones.
The calcium lost from our bones due to excessive protein has to go somewhere after it has served its purpose in our bloodstream, and so does the calcium we have ingested but have not been able to absorb due to high phosphorous/calcium ratios (the higher this ratio, the greater the loss of bone density). All this calcium ends up in our urine, producing very high levels of calcium in the kidney system, and all-too-often crystallizing into kidney stones.
Additionally, excessive protein consumption can cause the destruction of kidney tissue and the progressive deterioration of kidney function. Extra protein doesn't just trickle out of the body. It takes hard work on the part of the kidneys to get rid of the excess. Many animal studies to find out the relationship between the diet that is rich in protein and their kidneys have shown that the higher the protein in their diet, especially animal protein (i.e meat, fish and eggs), the greater the incidence and the more severe the cases of kidney hypertrophy and inflammation.
The same thing happen to human kidneys if we over consume aniamal protein. People who have suffered kidney damage or loss could preserve their remaining kidney function only if they put on a protein restricted diet. Those kidney patients whose protein intake is not restricted, and particularly those who continue to eat meat, show rapid deterioration of their kidneys to the point where many become dependent on kidney dialysis machines.
As a conclusion, excessive protein particularly animal protein in our daily diet does not only contribute to osteoporosis, but it is also a chief cause of crystallization of kidney stones, destruction of kidney tissue and progressive deterioration of kidney function.