Physiological Dysregulation After Vitamin D Abuse in Primary Hyperparathyroidism: An Emphasis on Dysfunction of the Calcium–PTH Axis
International Journal of Medical Toxicology and Forensic Medicine,
Vol. 16 (2026),
1 January 2026
,
Page 1-7
https://doi.org/10.22037/ijmtfm.v16.51811
Abstract
Background: Primary hyperparathyroidism (PHPT) patients frequently have vitamin D insufficiency, although vitamin D therapy is still debatable because of worries about aggravating hypercalcemia and hypercalciuria. This study examines the physiological effects of excessive vitamin D supplementation on the calcium-PTH axis in PHPT patients.
Methods: This retrospective investigation was performed on 68 PHPT patients. Our patients were split into two groups: the over-supplementation group (26) and the standard-dose group (42 patients). At baseline, one week, one month, two months, and four months after supplementation, serum ionized calcium (iCa), total calcium, PTH, phosphorus, fasting urine calcium/creatinine ratio (uCa/Cr), 25(OH)D, and 1,25(OH)₂D were measured.
Results: The 25(OH)D levels in the over-supplementation group rose from 14.8±4.2 ng/mL at baseline to 185.6±42.3 ng/mL at one week (p< 0.001). At one week, iCa increased considerably from 1.36±0.05 mmol/L to 1.53±0.09 mmol/L (p<0.001). uCa/Cr rose from 0.30±0.12 mg/mg to 0.52±0.18 mg/mg (p<0.001). At one week, PTH levels dropped from 158.4±45.6 pg/mL to 52.3±22.1 pg/mL (p< 0.001). There was no substantial hypercalcemia or PTH oversuppression in the standard-dose group, but there was a slight elevation in 25(OH)D (to 38.5±8.2 ng/mL).
Conclusion: Vitamin D over-supplementation in PHPT patients results in moderate, reversible hypercalcemia and hypercalciuria without renal damage, indicating that cautious, guideline-directed vitamin D replacement is safe in this population.
- Vitamin D, Calcium-PTH axis, Hypercalcemia, Primary hyperparathyroidism, Vitamin D toxicity
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References
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