It appears that the most critical time for pyramiding to develop is during the first year or two of a tortoise's life. If conditions are correct during the first year or two and pyramiding has not developed, then the chance of pyramiding developing in an older tortoise is greatly reduced even if husbandry conditions are not optimal.
For years there have been a number of opinions on the actual cause of pyramiding in tortoises. It had been pretty well assumed that excessive protein in the diet was the cause. Other factors including the ratio of calcium-to-phosphorus in the diet, temperature, access to natural light or UVB, dietary fiber and overfeeding were also cited as factors — most probably play a roll to one degree or another.