Different vitamin D substrate-product relationship after oral vitamin D supplementation in familial benign hypercalcemia, primary hyperparathyroidism, and healthy controls

Eur J Endocrinol. 2011 May;164(5):833-8. doi: 10.1530/EJE-10-1053. Epub 2011 Feb 10.

Abstract

Context: In healthy subjects and in patients with primary hyperparathyroidism (PH), the administration of a low dose of 25(OH)D (25 μg/day) increases the serum levels of both 25(OH)D and 1,25(OH)(2)D. It is unknown whether this relationship is present in patients affected by familial benign hypocalciuric hypercalcemia (FBH).

Objective: To evaluate the different vitamin D substrate-product relationship after oral vitamin D supplementation in familial benign hypercalcemia, PH, and healthy controls.

Design: We evaluated the main physiological regulators of 1α-hydroxylase and the substrate-product relationship of 25(OH)D and 1,25(OH)(2)D in 20 patients with PH, 25 with FBH, and 122 healthy sex- and age-matched controls before and after administration of 25(OH)D for 2 weeks.

Results: 25(OH)D increased significantly in all subjects, whereas 1,25(OH)(2)D serum levels increased significantly in PH patients and healthy controls but not in patients with FBH. Therefore, a significant positive substrate-product relationship of 25(OH)D-1,25(OH)(2)D was found in PH and healthy controls, but not in FBH. Monomeric calcitonin (hCT-M) was significantly lower at baseline and after 25(OH)D supplementation in the FBH group compared with the other two groups.

Conclusions: The lack of 1,25(OH)(2)D increase in FBH may be due to a direct inhibitory effect on 1α-hydroxylase of hypercalcemia per se, increased metabolic clearance of 1,25(OH)(2)D, or a decreased stimulus of 1α-hydroxylase related to persistently low levels of hCT.

Publication types

  • Comparative Study

MeSH terms

  • Administration, Oral
  • Aged
  • Dietary Supplements
  • Female
  • Humans
  • Hypercalcemia / blood
  • Hypercalcemia / congenital
  • Hypercalcemia / drug therapy
  • Hyperparathyroidism, Primary / blood*
  • Hyperparathyroidism, Primary / drug therapy*
  • Male
  • Middle Aged
  • Substrate Specificity
  • Vitamin D / administration & dosage*
  • Vitamin D / blood*

Substances

  • Vitamin D

Supplementary concepts

  • Hypocalciuric hypercalcemia, familial, type 1