Lead displaces calcium in the bones. Fluoride interferes with thyroid/parathyroid.
parathyroid regulates calcium, but kidney disfunction, and pancreatits can also be a cause. Urine tests and blood tests are both needed.
http://www.merck.com/mmhe/sec12/ch155/ch155b.html
Hypocalcemia most commonly results when too much calcium is lost in urine or when not enough calcium is moved from bones into the blood. Causes of hypocalcemia include the following:
A low level of parathyroid hormone (hypoparathyroidism), as can occur when the parathyroid glands are damaged during thyroid gland surgery
Lack of response to a normal level of parathyroid hormone (pseudohypoparathyroidism)
No parathyroid glands at birth
A low level of magnesium (hypomagnesemia), which reduces the activity of parathyroid hormone
Vitamin D deficiency (due to inadequate consumption or inadequate exposure to sunlight)
Kidney dysfunction (a common cause), which results in more calcium excreted in urine and makes the kidneys less able to activate vitamin D
Inadequate consumption of calcium
Disorders that decrease calcium absorption
Pancreatitis
Certain drugs, including rifampin Some Trade Names
RIFADINRIMACTANE
(an antibiotic), anticonvulsants (such as phenytoin Some Trade Names
DILANTIN
and phenobarbital Some Trade Names
LUMINAL
), bisphosphonates (such as alendronate Some Trade Names
FOSAMAX
, ibandronate Some Trade Names
BONIVA
, risedronate Some Trade Names
ACTONEL
, and zoledronic acid Some Trade Names
ZOMETA
), calcitonin Some Trade Names
MIACALCIN
, chloroquine Some Trade Names
ARALEN
, corticosteroids, and plicamycin