| Summary: | <p>Abstract</p> <p>Background</p> <p>Persons of Pakistani origin living in Oslo have a much higher prevalence of vitamin D deficiency and secondary hyperparathyroidism but similar bone mineral density compared with ethnic Norwegians. Our objective was to investigate whether Pakistani immigrants living in Oslo have an altered vitamin D metabolism by means of compensatory higher serum levels of 1,25-dihydroxyvitamin D (s-1,25(OH)<sub>2</sub>D) compared with ethnic Norwegians; and whether serum levels of ionized calcium (s-Ca<sup>2+</sup>) differ between Pakistanis and Norwegians.</p> <p>Methods</p> <p>In a cross-sectional, population-based study venous serum samples were drawn from 94 Pakistani men and 67 Pakistani women aged 30–60 years, and 290 Norwegian men and 270 Norwegian women aged 45–60 years; in total 721 subjects.</p> <p>Results</p> <p>Pakistanis had lower s-1,25(OH)<sub>2</sub>D compared with Norwegians (p < 0.001). Age- and gender adjusted mean (95% CI) levels were 93 (86, 99) pmol/l in Pakistanis and 123 (120, 126) pmol/l in Norwegians, p < 0.001. The difference persisted after controlling for body mass index. There was a positive relation between serum 25-hydroxyvitamin D (s-25(OH)D) and s-1,25(OH)<sub>2</sub>D in both groups. S-Ca<sup>2+ </sup>was higher in Pakistanis; age-adjusted mean (95% CI) levels were 1.28 (1.27, 1.28) mmol/l in Pakistanis and 1.26 (1.26, 1.26) mmol/l in Norwegians, p < 0.001. In both groups, s-Ca<sup>2+ </sup>was inversely correlated to serum intact parathyroid hormone levels (s-iPTH). For any s-iPTH, s-Ca<sup>2+ </sup>was higher in Pakistanis, also when controlling for age.</p> <p>Conclusion</p> <p>Community-dwelling Pakistanis in Oslo with low vitamin D status and secondary hyperparathyroidism have lower s-1,25(OH)<sub>2</sub>D compared with ethnic Norwegians. However, the Pakistanis have higher s-Ca<sup>2+</sup>. The cause of the higher s-Ca<sup>2+ </sup>in Pakistanis in spite of their higher iPTH remains unclear.</p>
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