Damn Zach.....now you are making me work after hours as well!
Short answer: we don't fully know.
Longer answer: Senspar is a "calcimimetc"...it makes the Calcium sensing receptors in the body (on the Parathyroid gland, in the gut, etc...) more sensitive to calcium. So it fools the various organs of the body to think the Calcium level is higher than it really is. In turn, this tells those organs to turn off the signals and mechanisms to raise calcium. So instead of having PTH levels rise, they now fall. Instead of the gut absorbing more calcium, it absorbs less, leading to lower calcium levels in the blood.
But the flip side is that this may go too far and the body may need higher blood calcium levels, but with sensipar, it is fooled into thinking the calcium level is OK.
Truth is that we have only begun to understand Calcium, phosphorus, and PTH regulation.
But it makes a good story though.....