These are cocrystallizations of potassium sulfate and sulfates of magnesium calcium and sodium. Problems with blood levels of potassium, magnesium and calcium may also contribute. Calcium and potassium salts are also permitted. Some small effects occur on calcium and potassium levels. It is partly responsible for the regulation of potassium, sodium, calcium, and pH. Vitamin D is involved in calcium and phosphate regulation. Imbalances in calcium and phosphorus levels can result in various skeletal complications. It has higher levels of protein, thiamine, riboflavin, phosphorus, calcium, and iron than wheat flour. Echinoderms typically possess an internal skeleton composed of plates of calcium carbonate. Other factors may include not enough calcium or phosphorus. Increasing dietary calcium results in minor increases in blood calcium. They are oval structures densely packed with elliptical calcium carbonate crystals. Iron, calcium, and phosphorus become more abundant. All birds lay amniotic eggs with hard shells made mostly of calcium carbonate. When alive, corals are colonies of small animals embedded in calcium carbonate shells.