Hey Vispares,

Thanks for the wonderful update and lab data.  I love success stories like this.

For starters, you should be able to stop the vitamin B 50 in a few weeks.  You only need to take it for 3 months.

You can also drop your vitamin D3 intake to 15,000 IU/day for 10 days to two weeks...  If the beast stays away, drop it again to a maintenance dose of 10,000 IU/day.  That should also bring your 25(OH)D down around 80 ng/mL. 

If you start getting hit again, no worry...  Just take a 50,000 IU loading dose of vitamin D3 and up your maintenance dose to 15,000 IU/day.

The rest of your regimen should stay the same...

Take care and please keep us posted.

V/R, Batch

Vispares,

The 25(OH)D serum concentration most frequently associated with vitamin D3 intoxication is 200 ng/mL, (500 nmol/L).  That said, there are several vitamin D3 experts who claim the real serum concentration of 25(OH)D where vitamin D3 toxicity likely occurs is around 300 ng/mL, (750 nmol/L).

The important thing to remember is the 25(OH)D serum concentration is only a bio-marker.  The only accepted indication of actual vitamin D3 intoxication is an elevated serum calcium concentration above its normal reference range.

We've had several CH'ers report maintaining their serum 25(OH)D up around 190 ng/mL while under a physician's supervision with frequent lab tests for serum 25(OH)D, PTH and calcium.  No elevated serum calcium reported...

Hope this helps.

Take care.

V/R, Batch

Hola Vesperas,

Thanks for the update and good question. 
Once vitamin D3 is metabolized to 25(OH)D3, (calcidiol), by the liver, further metabolism to 1,25(OH)2D3 can take two different paths. 

The following chart illustrates the endocrine path through the kidneys and the extrarenal (outside the kidneys) autocrine path that takes place at the cellular and nuclear level throughout the body including the trigeminal ganglia.

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The production of serum 1,25(OH)2D3 is tightly controlled by calcium homeostasis.  When serum calcium drops towards the low end of its normal reference range, the parthyroids sense this condition and secretes the parathyroid hormone (PTH). 

This hormone triggers the kidneys to produce more of the 1 α Hydroxylase enzyme that metabolizes 25(OH)D3 to 1,25(OH)2D3, (calcitriol). The increased serum concentration of calcitriol pulls more calcium from the gut increasing calcium serum concentration.

When the serum calcium concentration approaches the upper limit of its normal reference range, the parathyroids sense this condition and slows production of PTH so the kidneys produce less calcitriol.

Diagnostic lab tests like yours, measure the serum concentration of 1,25(OH)2D3, calcidiol produced in the endocrine path of vitamin D3 metabolism.  Calcitriol produced along the autocrine path of vitamin D3 metabolism remains within the cells and never enters the bloodstream so cannot be measured.

Soooo... after that long winded explanation of vitamin D3 pharmacokinetics, the simple answer to your question is it is very normal to have your serum concentration of 25(OH)D go up... and as long as your serum calcium levels are normal... the serum concentration of 1,25(OH)2D3, calcitriol will be low.

Hope this helps.

Take care,

V/R, Batch