The study looked at how the body regulates calcium levels when deprived of calcium for a long time. They focused on the roles of bones and kidneys in this process. By removing the parathyroid glands, they found that in rats on a low calcium diet, the kidneys played a bigger role in maintaining calcium levels compared to rats on a normal diet. In rats deprived of calcium, bones became more important in regulating calcium levels. This shows that when calcium is scarce, the body shifts its focus from the kidneys to the bones to keep calcium levels stable.