Name at least two hormones which result in the fluctuation of $Ca^{++}$ levels.

(N/A) The two primary hormones responsible for regulating $Ca^{++}$ levels in the blood are Parathyroid hormone $(PTH)$ and Calcitonin.
$PTH$ is secreted by the parathyroid gland and acts to increase blood $Ca^{++}$ levels. It stimulates bone resorption (demineralization),increases $Ca^{++}$ reabsorption by renal tubules,and enhances $Ca^{++}$ absorption from digested food in the intestine.
Calcitonin is produced by the parafollicular cells ($C$-cells) of the thyroid gland. It acts antagonistically to $PTH$ by lowering blood $Ca^{++}$ levels,primarily by inhibiting bone resorption.