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It's because he was diagnosed before with sarcoidosis. It can have an impact on both vitamin D and calcium.

Which is plausibly why she tried using those agents to poison him: instead of being suspicious it was seen as a very complicated medical case.

Here's what I asked sonnet for a friend:

---

Here's an ASCII diagram illustrating the relationship:

                  Sarcoidosis
                       |
                       v
                   Granulomas
                       |
                       v
              1-alpha-hydroxylase ↑
                       |
                       v
    25(OH)D ---------> 1,25(OH)2D ↑
      ^                    |
      |                    v
Vitamin D3 <-------- Calcium absorption ↑

                           |
                           v
                    Serum Calcium ↑

                           |
                           v
                    Hypercalcemia
Explanation for a 3rd-year medical student:

- Sarcoidosis is a granulomatous disease characterized by the formation of granulomas in various organs, particularly the lungs.

- These granulomas contain activated macrophages that express high levels of 1-alpha-hydroxylase, the enzyme responsible for converting 25-hydroxyvitamin D (25(OH)D) to its active form, 1,25-dihydroxyvitamin D (1,25(OH)2D).

- The increased 1-alpha-hydroxylase activity leads to excessive production of 1,25(OH)2D, which is not regulated by the normal feedback mechanisms.

- 1,25(OH)2D enhances intestinal calcium absorption and bone resorption, leading to increased serum calcium levels.

- This process can result in hypercalcemia, a common complication in sarcoidosis patients.

- The excess 1,25(OH)2D also suppresses parathyroid hormone (PTH) production, which normally regulates calcium homeostasis.

- Importantly, the increased 1,25(OH)2D levels are not dependent on vitamin D intake or sun exposure, as the conversion occurs independently of the body's vitamin D status.

- This dysregulation can lead to a paradoxical situation where patients with sarcoidosis may have high 1,25(OH)2D levels but low or normal 25(OH)D levels.

Key points to remember:

- Granulomas in sarcoidosis are the source of increased 1-alpha-hydroxylase activity.

- This leads to excessive 1,25(OH)2D production, independent of normal regulatory mechanisms.

- The result is increased calcium absorption and potential hypercalcemia.

- Management often involves limiting calcium and vitamin D intake, and in some cases, using corticosteroids to suppress granuloma activity.



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