(Is my PTH is not responding or is it got suppressed by the use of Calcitriol?)
Recently when I got my blood tests done, the calcium and PTH (Parathytoid hormone) levels of my blood observed little lower than the normal range. PTH is inversely proportional to Calcium. So when calcium falls then PTH should increase. Whereas, both PTH & Ca found to be low in my case. Why?
Blood tests Dtd.10/10/2012
My Calcium: 8 mg/dl (Target Calcium - 8.5 to 10.5 mg/dl.)
My PTH: 71 pg/ml (Target PTH in Stage-5, CKD: 150-300 pg/mL)
Something important to know in general for all:
Calcium: is the most plentiful mineral in the body that is essential for building new bone cells and keeping existing bones strong and also to keep the nerves function properly. If calcium levels in the blood become too low, the parathyroid glands (four small glands at neck) release a hormone called parathyroid hormone (PTH). This hormone regulates calcium levels in the blood.
Vitamin D: Healthy kidneys activate vitamin D. The activated form of vitamin D is called calcitriol. Calcitriol helps the body absorb calcium. Working together, calcitriol helps maintain normal parathyroid hormone (PTH) levels, and they carefully balance calcium in our system (Body).
If blood calcium levels are too low (either it may be due to vitamin D deficiency or low calcium intake with food or for any other reasons like kidney failure) the PTH hormone will begin removing calcium from the bones to get calcium blood levels back to normal. Over months and years to this effect, as calcium is stripped from the bones, this can make the bones weak, so their texture becomes more like a piece of chalk than of a sturdy bone.
So to understand in a simpler way, the body needs Vitamin D, Healthy Kidneys and active PTH gland to maintain normal levels of calcium in the blood.
For the people on Dialysis:
When kidneys fail, they stop converting inactive vitamin D to calcitriol. The result is your body is unable to absorb calcium from food, so it “borrows” the calcium it needs from the greatest calcium storage depot — the bones as described in the previous paragraph.
Doctors prescribe Kidney disease patients (whose kidneys aren’t making enough calcitriol) a special “active vitamin D” supplement, and may also prescribe a calcium supplement if needed. On the other hand, once the calcium level is high, your doctor may withhold vitamin D therapy until calcium levels are back to normal. Because with too much Calcium in the blood, the Calcium starts getting deposited on the walls of your veins and arteries leading to vascular calcification which can be fatal if not corrected in time.
Now coming to my case:
Few months back during my routine consultation with nephrologist, I was complaining about body and muscular pains. My calcium was normal but nearer to the lower side of the range and PTH was not tested then. My doctor prescribed calcitriol (active vitamin D” supplement) also suggested me to come with PTH report in the next month’s visit. This may be attributing to secondary hyperparathyroidism ‘low calcium and high PTH’, which is a long term side effect of kidney disease. The idea might be, “Calcitriol increases Calcium absorption and also decreases PTH”.
But recently when I did my blood tests, the reports come out with both calcium and PTH low. And subsequently when I consulted the doctor, he stopped me to continue Calcitriol and asked me to start another supplement that is Calciriol granules (which is basically Inactive Vitamin D3 – Cholecalciferol ). Hopefully this should help my calcium to increase and PTH to settle at a normal value that assigned to ESRD folks.
Why my PTH fall to a low value when the Calcium is Low? And where the mistake took place?
I think by taking the Calcitriol(Vitamin D3) my PTH gland got suppressed its ability to regulate calcium levels in the blood as Calcitriol decreases PTH. If had I got tested my PTH at the first instant and as it would come normal, my doctor should not have prescribed Calcitriol at all and instead he should have prescribed some calcium supplements to increase my calcium levels in the blood. Since I have stopped the Calcitriol now, hopefully my PTH will raise its head and work normally to regulate blood calcium value to the required level.
But still I did not understand one thing is that if I stop calcitriol while living with failed Kidneys, how vitamin D will activate and help my body to absorb enough calcium? Because only Healthy kidneys can activate vitamin D that we get either from food or sunlight further enabling body to absorb calcium.
Ahhh! for me It’s been quite tiring to keep thinking about all this for some time. Now I decided not to worry too much and just leave it to my nephrologist during my next visit.
