--I'm quite familiar with that site.

My Vitamin D levels--at least the D-25 levels--are right at the low end of normal (30.3, with the low end of the reference range 30). I'm waiting for results of the D-1_25 OH levels, which should be higher. This is consistent, as the site says, with higher calcium levels signalling the body's intestines to absorb less vitamin D in trying to keep the calcium levels from going too high. From a causal perspective, consistent with parathyroid adenoma. (Admittedly, there are many doctors who don't understand the point the site's authors are trying to make.)