Hypomagnesemia results in decreased PTH secretion as well as resistance to PTH action at the receptor.[7,37] Vitamin D deficiency reduces gastrointestinal calcium absorption as well as kidney reabsorption of calcium.[7,37] Vitamin D deficiency and hypomagnesemia is highly prevalent in patients with malignancy which can be secondary to medications and malnutrition. This evidence concerns the gene PTH and familial primary hypomagnesemia.