I have found interesting reasons why our VitD is low and possible cause for our issue.
1- Vit D induces P450 (CYP3A4) enzyme. If Vit D is low then P450 will be low too. Also this is the enzyme which clears many hormones are meds from the body.
2- There are two main reasons for low VitD: hyperparathyroidism and low kidney function (supposing we have no problem with food or sunlight).
if Vit D is low then Calcium should be low or on the low normal side.Because this mean due to low VitD intestines are not absorbing VitD.
But if Vid D is low and Calcium is high or high normal then it is a big red flag.This mean parathyroid hormone is knocking out calcium from bones into the blood, when body sees high calcium in the blood it tries to decrease absorption of calcium from intestines by reducing VitD.This is why our Vit D is constantly low.
Here is more detail
parathyroid.com/low-vitamin-d.htm
The following graph illustrates that there are two causes of Low Vitamin D: The first is that it is just low because you aren’t getting enough of it in your diet and/or you are not going outside enough (vitamin D is made in our skin when exposed to the sun) (the yellow blob). The second reason for a low vitamin D is that you have primary hyperparathyroidism due to a small tumor in your neck and the body shuts down the vitamin D
with primary hyperparathyroidism calcium levels between 10.2 mg/dl and 11.4 mg/dl, and Vitamin D levels between 8.5 ng/ml and 33.1 ng/ml. (key point vit D tool low and blood calcium high)
If you really have low vitamin D (and not a parathyroid tumor), for which your doctor may want to give you vitamin D pills, then you should have a normal or LOW blood calcium
Here is the most important fact on this page: since vitamin D is required for humans to absorb calcium in their intestines, a low vitamin D cannot ever be the cause of high blood calcium. This fact is not debatable. Thus, if you have a low vitamin D and your calcium is above 10.0, then the high calcium in your blood must have come from somewhere else other than your diet (it came from your bones). Thus, if you have a low vitamin D, and a calcium level above 10.1, then you are almost guaranteed to have primary hyperparathyroidism and need surgery to remove the parathyroid tumor. A low vitamin D cannot ever be the cause of high blood calcium. Keep reading, because most doctors get confused between the yellow and the blue blobs.
**If you are over 35 years of age, and your blood calcium is high (over 10.1 mg/dl) you are almost certain to have primary hyperparathyroidism. If your blood calcium is high and your vitamin D level is low, then you are almost guaranteed to have a parathyroid tumor (primary hyperparathyroidism)
Why body keeps low Vit D in case of parathyroidism
Hyperparathyroidism is associated with high calcium in the blood. The cause is a parathyroid tumor. This is discussed throughout this website, so we will not go into it here. Basically, a tumor grows from one of your parathyroid glands… this tumor produces parathyroid hormone which takes calcium out of your bones and puts it into your blood. You get osteoporosis and feel bad because of the high calcium in the blood.
The body doesn’t want the calcium to be high… So, it will try to get rid of the calcium in the urine… which is why many patients (about 1/3) will have high calcium in the urine (they can get kidney stones from this).
The body also wants to shut down calcium absorption from your intestines. It does this by limiting the amount of Vitamin D in your body. Thus, if your body determines that your calcium is too high… it can decrease the amount of calcium that is absorbed from your intestines by decreasing the amount of Vitamin D available. If your Vitamin D levels are decreased, you can’t absorb so much calcium from your diet. This is a protective measure.
The bottom line again: If your calcium is high, you almost certainly have a parathyroid tumor. If your calcium is high and your Vitamin D is low, you STILL have a parathyroid tumor. If your calcium is high and your Vitamin D is normal, you STILL have a parathyroid tumor. When you get your parathyroid tumor removed, your Vitamin D level will almost always correct itself within a few months.