Clinical Significance of Vitamin D Deficiency in Primary Hyperparathyroidism, and Safety of Vitamin D Therapy

Nasser Mikhail, MD, MSc

Disclosures

South Med J. 2011;104(1):29-33. 

In This Article

Characteristics of Primary Hyperparathyroidism Complicated by Vitamin D Deficiency

Overall, hypovitaminosis D is associated with a more severe form of PHPT in terms of biochemical and possibly bony features. This observation is not unexpected, because vitamin D deficiency per se is known to stimulate PTH secretion, causing secondary hyperparathyroidism which may be additive to the pre-existing PHPT.[15] Retrospective studies from the US showed that patients with PHPT having vitamin D deficiency, defined as serum 25-OHD levels <15 ng/mL, <20 ng/mL, or <25 ng/mL had higher circulating levels of PTH, calcium, and alkaline phosphatase, and greater parathyroid adenoma weight compared with their vitamin D-sufficient counterparts.[9,16–18] Moreover, low serum levels of 25-OHD were shown to be related to persistent elevation of PTH after parathyroidectomy in some, but not all studies.[17–19]

Data regarding the relationship between serum 25-OHD values and bony manifestations of PHPT were inconsistent. In a series of 243 consecutive patients with PHPT, Moosgard et al[20] found that low serum levels of 25-OHD were associated with decreased bone mineral density (BMD) in the forearms, femoral neck, and whole body, independently of PTH levels. Conversely, in a smaller cross-sectional study, Carnevale et al[21] did not find a significant correlation between 25-OHD plasma levels and BMD at the lumbar spine and femoral neck in 62 women with PHPT. While no significant association was found between serum levels of 25-OHD and the prevalence of fractures in the cross-sectional study of Moosgard et al,[20] one retrospective study from Sweden showed that low serum levels of 25-OHD3 in the 10-year period preceding parathyroidectomy were an independent risk factor for the occurrence of fractures.[22] With respect to the possible link between vitamin D deficiency and renal complications of PHPT, available data suggest no significant difference in urinary calcium excretion or in the occurrence of kidney stones between patients with and without vitamin D deficiency.[5,17]

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