A polypeptide causing decrease in serum calcium is:
I. Calcitonin is a hypocalcemic peptide hormone that acts as the ‘physiologic-antagonist’ to parathyroid hormone.
II. The hypocalcemic activity is accounted for primarily by inhibition of osteoclast-mediated bone resorption and secondarily by stimulation of renal calcium clearance.
III. These effects are mediated by receptors on osteoclasts and renal tubular cells.