after sensing a drop in calcium levels in the body,parathyroid hormone from the parathyroid glands will be secreted in a negative feedback mechanism of homeostasis
first the parathyroid hormone stimulates release of calcium ions from the bone through the process of bone reorption
then the parathyroid hormone will reduce urinary excretion of calcium by increasing its re absorption in the nephron
finally , the parathyroid hormone will increase the rate of vitamin d synthesis in the small intestine to yield more calcium