Vitamin D Council and brief quote on Vit D in sarcoidosis
The Vitamin Di Council is an excellent source of information on Vitamin D, health and science (thanks Reenie:).
Hypersensitivity, Not Toxicity
Vitamin Di hypersensitivity syndromes are often mistaken for vitamin D toxicity. The most common is primary hyperparathyroidism. Other syndromes occur when abnormal tissue subverts the kidney's normal regulation of endocrine calcitriol production. Aberrant tissues, usually granulomatous, convert 25(OH)D into calcitriol causing high blood calcium. The most common such condition is sarcoidosis, oat cell carcinoma of the lung and non‑Hodgkin's lymphoma but other illness can cause the syndrome and they can occur while the patient's 25(OH)D levels are normal or even low. For that reason, while rare, it is advisable to seek a knowledgeable physician's care when repleting your vitamin D system, especially if you are older, have sarcoidosis, cancer or other granulomatous diseasesii. In such high‑risk patients, periodic monitoring of 25(OH)D levels and serum calcium will alert the physician to the need to do more tests, such as calcitriol or PTH, and take further action.
However, it seems clear that restoring physiological serum levels of 25(OH)D will help many more patients that it will hurt. In fact, living in America today while worrying about vitamin D toxicity is like dying of thirst in the desert while worrying about drowning.