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Primary hyperparathyroidism and severe hypercalcemia with low circulating 1,25-dihydroxyvitamin D
J L Shaker1, K W Krawczyk, J W Findling
1Department of Medicine, St. Luke's Medical Center, Milwaukee, Wisconsin 53215.
The Journal of Clinical Endocrinology and Metabolism
|November 1, 1990
Summary
Primary hyperparathyroidism (PHPT) can present with low vitamin D levels despite high calcium intake. Reducing calcium intake normalized vitamin D and parathyroid hormone levels in a patient with PHPT.
Area of Science:
- Endocrinology
- Metabolic Bone Disease
Background:
- Primary hyperparathyroidism (PHPT) is characterized by excessive parathyroid hormone (PTH) secretion.
- Hypercalcemia is a hallmark of PHPT, often influenced by calcium intake and vitamin D metabolism.
Observation:
- A postmenopausal woman with PHPT and severe hypercalcemia presented with a low serum 1,25-dihydroxyvitamin D [1,25-(OH)2D] level (17 pmol/L) despite a high daily calcium intake (>2 g).
- Her intact PTH level was markedly elevated.
Findings:
- Reducing dietary calcium intake normalized serum calcium levels.
- Concurrently, serum 1,25-(OH)2D increased significantly (to 122 pmol/L), and intact PTH decreased to 32% of baseline.
- This suggests a potential direct effect of severe hypercalcemia on vitamin D levels in PHPT.
Implications:
- PHPT can be associated with suppressed 1,25-(OH)2D levels.
- Low 1,25-(OH)2D in PHPT may be reversible upon correction of hypercalcemia.
- This highlights the complex interplay between calcium homeostasis, PTH, and vitamin D in endocrine disorders.