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    Bone Mineral Density and Testicular Failure: Evidence for a Role of Vitamin D 25-Hydroxylase in Human Testis

    J Clin Endocrinol Metab. 2011 Jan 26. [Epub ahead of print]

    The authors examined the role of CYP2R1 (Vitamin D, 25-hydroxylase) in males with hypospermia for a variety of reasons. In all patients 25-hydroxyvitamin D levels were significantly lower and PTH levels higher compared to controls and CYP2R1 were decreased at the mRNA and protein level in the testies. In addition, the patients had decreased bone mass despite normal testosterone levels.
    Authors: Foresta C, Strapazzon G, De Toni L, et. al

    Working Hypothesis: Mutations in the CYP2R1 gene, highly expressed in the testis and encoding vitamin D 25-hydroxylase, result in a vitamin D deficiency and a defective calcium homeostasis leading to rickets. Objective: Our aim was to investigate CYP2R1 expression in pathological testis samples and relate this to vitamin D metabolism in testiculopathic patients. Design, Patients, Setting: Testis samples for in vitro study and 98 young men were transversally evaluated at Padova's Center for Male Gamete Cryopreservation. Methods: CYP2R1 mRNA expression and protein production were evaluated by quantitative RT-PCR, Western blot analysis, and immunofluorescence. Hormonal and bone-marker levels, and bone densitometry by dual-energy x-ray absorptiometry, were determined in patients with Sertoli-cell-only syndrome and severe hypospermatogenesis. Results: We found a lower gene and protein expression of CYP2R1 in samples with hypospermatogenesis and Sertoli-cell-only syndrome (P < 0.05) and a colocalization with INSL-3, a Leydig cell marker, at immunofluorescence. In all testiculopathic patients 25-hydroxyvitamin D levels were significantly lower and PTH levels higher compared to controls (P < 0.05). Furthermore, testiculopathic patients showed osteopenia and osteoporosis despite normal testosterone levels compared with controls both with increased bone-marker levels and altered dual-energy x-ray absorptiometry in the femoral neck and lumbar spine (for all parameters, P < 0.05). Conclusions: Our data show an association between testiculopathy and alteration of the bone status, despite unvaried androgen and estrogen levels and no other evident cause of vitamin D reduction. Further studies in larger cohorts are needed to confirm our results.

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