If blood calcium levels drop, the parathyroid gland releases thehormone called  ____________ . This hormone has multipleeffects.
(1) The hormone stimulates bone cells to break down bone tissueand  ____________  calcium ion into theblood.
(2) The hormone stimulatesthe  ____________  to conserve calcium ions,preventing their excretion, and to activatevitamin  ____________  which increases calciumuptake from the diet.
(3) The hormone increasesthe  ____________  of calcium from theintestines.
The result of the these hormonal effects isto  ____________  blood calcium levels.
