An unique form of osteomalacia associated with end organ refractoriness to 1,25-dihydroxyvitamin D and apparent defective synthesis of 25-hydroxyvitamin D

J. E. Zerwekh, K. Glass, J. Jowsey, C. Y C Pak

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A 28-yr-old woman presented with hypocalcemia, hypophosphatemia, secondary hyperparthyroidism, and biopsyproven osteomalacia despite treatment with vitamin D2, (17.5 mg/day). Three weeks after vitamin D2 treatment was stopped, she was found to have a low normal serum 25-hydroxyvitamin D (25OHD) and high serum 1α,25-dihydroxyvitamin D [1,25(OH)2D] of 18.6 ng/ml and 21.2 ng/dl, respectively. The fractional intestinal calcium absorption was low at 0.26. Treatment with 25OHD3 (20-50 μg/day) corrected the hypocalcemia and secondary hyperparathyroidism, raised intestinal calcium absorption, and reversed the skeletal lesions of osteomalacia. Serum 25OHD concentration rose to 51 ng/ml, while 1,25(OH)2D remained elevated. This case illustrates the probable operation of dual abnormalities in vitamin D metabolism. An impaired end organ responsiveness to 1,25(OH)2D was suggested by a low intestinal calcium absorption in the face of high serum 1,25(OH)2D. Moreover, there may have been a defective vitamin D-25-hydroxylase, since there was a relative refractoriness to treatment with large doses of vitamin D2, an inappropriately low serum 25OHD after vitamin D2 therapy, and a responsiveness to treatment with 25OHD3.

Original languageEnglish (US)
Pages (from-to)171-175
Number of pages5
JournalJournal of Clinical Endocrinology and Metabolism
Issue number2
StatePublished - Aug 1979


ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Endocrinology
  • Clinical Biochemistry
  • Biochemistry, medical

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