Urinary calcium to creatinine ratio: a potential marker of secondary hyperparathyroidism in patients with vitamin D-dependent rickets type 1A.

Abstract

Patients with vitamin D-dependent rickets type 1A (VDDR1A) are usually treated with alfacalcidol, an analog of vitamin D. Around puberty, an increased dose of alfacalcidol is recommended for these patients to avoid hypocalcemia and secondary hyperparathyroidism. However, no indicators of secondary hyperparathyroidism except for PTH are presently known. The aim of this study is to evaluate whether urinary calcium to creatinine ratio (U-Ca/Cr) is useful as a biomarker of secondary hyperparathyroidism in VDDR1A patients in order to determine the proper dose of alfacalcidol. Two brothers with VDDR1A were recruited who had null mutations of CYP27B1 which encodes 1-alpha-hydroxylase of vitamin D. We investigated the relationship between U-Ca/Cr and intact-PTH around puberty when the brothers showed hypocalcemia with secondary hyperparathyroidism. The results were compared to those of five patients with vitamin D deficiency (VDD). As a result, high intact-PTH levels were observed when U-Ca/Cr decreased to less than 0.1 (mg/mg) in both VDDR1A brothers. This relationship was also observed in the VDD patients. However, it is necessary to take into account body calcium status, either in depletion or in excess, to accurately evaluate the relationship between U-Ca/Cr and secondary hyperparathyroidism. First, low U-Ca/Cr was detected in situations with calcium depletion without hyperparathyroidism in the VDDR1A patients. Second, high U-Ca/Cr with hyperparathyroidism could be detected theoretically in a condition of excess calcium supply. In conclusion, a U-Ca/Cr ratio of less than 0.1 (mg/mg) in VDDR1A patients is useful to accurately evaluate calcium depletion and secondary hyperparathyroidism.

• Authors: Kentaro Miyai, Toshikazu Onishi, Kenichi Kashimada, Yukihiro Hasegawa
• Journal: Endocrine journal (Endocr J) Vol. 62 Issue 1 Pg. 61-8 ( 2015) ISSN: 1348-4540 [Electronic] Japan
• PMID: 25284246 (Publication Type: Case Reports, Journal Article)

Chemical References

• Biomarkers
• PTH protein, human
• Parathyroid Hormone
• Creatinine
• 25-Hydroxyvitamin D3 1-alpha-Hydroxylase
• CYP27B1 protein, human
• Calcium

Topics

• 25-Hydroxyvitamin D3 1-alpha-Hydroxylase (genetics)
• Algorithms
• Biomarkers (urine)
• Calcium (urine)
• Child
• Creatinine (urine)
• Down-Regulation
• Familial Hypophosphatemic Rickets (genetics, physiopathology)
• Family Health
• Frameshift Mutation
• Heterozygote
• Humans
• Hyperparathyroidism, Secondary (blood, diagnosis, etiology, urine)
• Male
• Mutation, Missense
• Parathyroid Hormone (blood)
• Puberty
• Siblings