What is the relation between secretion of parathormone and the calcium blood level?
The parathormone enhances the calcium blood level as it stimulates the resorption (remodelation) of the osseous tissue. When osteoclasts remodel bones calcium is released in the circulation.
Parathormone also acts enhancing the calcium absorption in the intestines by vitamin D activation. It acts in the kidneys promoting tubular calcium resorption too.