Serum calcium levels are controlled by a number of factors, including diet, Vitamin D, and parathyroid gland and kidney function. Calcium levels are routinely measured to assess kidney problems, bone conditions, and parathyroid gland function. Calcium levels are also measured to investigate kidney stones and certain neurological disorders accompanied by cramps.
Hypercalcemia (abnormally high blood calcium levels) can be caused by overactive parathyroid glands, which secrete parathyroid hormone (PTH), or by excessive Vitamin D, or by cancer with bone metastases. Other causes include an overactive thyroid gland, sarcoidosis, and certain medications.
Hypocalcemia (an abnormally low blood calcium level) is often caused by a low level of albumin in the blood (liver disease or malnutrition). This is actually a “false” hypocalcemia, which can be compensated by mathematically correcting for the low albumin levels. Other causes range from underactive parathyroid glands to kidney disease (kidney failure) or severe Vitamin D deficiency.