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Context: Patients with 25-hydroxyvitamin D deficiency (25OHD <20 ng/ml) and primary hyperparathyroidism (PHPT) have more severe disease reflected by higher serum PTH levels compared to those with vitamin D levels in the insufficient (20-29 ng/ml) or replete range (≥ 30 ng/ml)., Objective: To study the effect of low vitamin D in PHPT on volumetric bone mineral density (vBMD), bone microarchitecture, and bone strength., Design, Setting, and Participants: This is a cross-sectional analysis of 99 PHPT patients with and without 25OHD insufficiency and deficiency from a university hospital., Outcome Measures: Bone microarchitecture and strength were assessed with high-resolution peripheral quantitative computed tomography (HRpQCT), microfinite element analysis, and individual trabecula segmentation., Results: In this cohort, 25OHD levels were deficient in 18.1%, insufficient in 35.4% and replete in 46.5%. Those with lower 25OHD levels had higher PTH (P < .0001), were younger (P = .001) and tended to weigh more (P = .053). There were no age-, weight- and sex-adjusted between-group differences (<20 vs 20-29 vs ≥ 30 ng/ml) in any HRpQCT, microfinite element analysis, or individual trabecula segmentation indices. Because few participants had 25OHD below 20 ng/ml, we also compared those with 25OHD below 30 vs at least 30 ng/ml and found only a trend toward lower adjusted cortical vBMD (3.1%, P = .08) and higher cortical porosity (least squares mean ± SEM 7.5 ± 0.3 vs 6.6 ± 0.3%, P = .07) at the tibia but not the radius. Stiffness did not differ at either site. In multiple regression analysis, 25OHD accounted for only three of the 49.2% known variance in cortical vBMD; 25OHD was not significant in the model for cortical porosity at the tibia., Conclusion: Low 25OHD levels are associated with higher PTH levels in PHPT, but contrary to our hypothesis, these differences did not significantly affect vBMD or microarchitecture, nor did they result in lower stiffness. Low vitamin D in PHPT using current 25OHD thresholds for insufficiency and deficiency did not significantly affect skeletal integrity as assessed by HRpQCT.

Context: Seasonal variability in 25-hydroxyvitamin D [25(OH)D] and PTH levels in the general population has been associated with differences in bone turnover markers, bone density, and fracture risk. Seasonal variability in 25(OH)D and PTH levels has also been reported in primary hyperparathyroidism (PHPT)., Objective: Given the widespread use of vitamin D supplements, we sought to determine whether patients with PHPT still demonstrated seasonal variation in 25(OH)D levels., Design and Setting: This cross-sectional study was conducted at a university medical center at a Northeastern U.S. latitude (New York, NY)., Patients: One hundred patients with PHPT participated in the study., Outcome Measures: We assessed vitamin D supplement use and seasonal variation in serum 25(OH)D., Results: Patients had PHPT ([mean ± SD] calcium, 10.8 ± 1.0 mg/dL; PTH, 85 ± 48 pg/mL) with a mean 25(OH)D level of 29 ± 10 ng/mL. Although only one fifth of participants had vitamin D deficiency (19% < 20 ng/mL), more than half were either deficient or insufficient (54% < 30 ng/mL). Sun exposure varied by season, but there were no seasonal differences in levels of 25(OH)D, PTH, bone markers, or bone mineral density, or in the prevalence of 25(OH)D less than 20 or less than 30 ng/mL. Most of the participants (65%) took supplemental vitamin D (dose among users: mean, 1643 ± 1496 IU; median, 1000 IU daily), and supplement users had markedly better vitamin D status than nonusers (25(OH)D < 20 ng/mL: 8 vs 40%; P < .0001; < 30 ng/mL: 40 vs 80%; P = .0001; ≥ 30 ng/mL: 60 vs 20%; P = .0001)., Conclusions: We found no evidence of seasonal variation in 25(OH)D levels or PHPT disease severity in the Northeastern United States. This change is likely due to widespread high vitamin D supplement intake, which has resulted in better vitamin D status among supplement users and can mask the effect of season on serum 25(OH)D levels.

Context: Vitamin D (25-hydroxyvitamin D [25OHD]) deficiency (<20 ng/mL) and insufficiency (20-29 ng/mL) are common in primary hyperparathyroidism (PHPT), but data regarding their skeletal effects in PHPT are limited., Objective: The objective was to evaluate the association between 25OHD levels and PHPT severity., Design, Settings, and Participants: This is a cross-sectional analysis of 100 PHPT patients with and without 25OHD insufficiency and deficiency from a university hospital setting., Outcome Measures: We measured calciotropic hormones, bone turnover markers, and bone mineral density (BMD) by dual x-ray absorptiometry., Results: Lower 25OHD was associated with some (PTH: r = -0.42; P < .0001; 1,25-dihydroxyvitamin D: r = -0.27; P = .008; serum PO4: r = 0.31; P = .002) but not all (serum/urine calcium) indicators of PHPT severity. Lower 25OHD was also associated with younger age, higher body mass index, male gender, better renal function, and lower vitamin D intake. Comparison of those with deficient (<20 ng/mL; 19%) vs insufficient (20-29 ng/mL; 35%) vs replete (≥30 ng/mL; 46%) 25OHD demonstrated more severe PHPT as reflected by higher PTH (mean ± SEM, 126 ± 10 vs 81 ± 7 vs 72 ± 7 pg/mL; P < .0001) but no difference in nephrolithiasis, osteoporosis, fractures, serum or urinary calcium, bone turnover markers, or BMD after adjustment for age and weight. In women, T-scores at the 1/3 radius were lower in those with 25OHD of 20-29 ng/mL, compared to those who were vitamin D replete (P = .048). In multiple regression modeling, 25OHD (but not PTH) was an independent predictor of 1/3 radius BMD., Conclusion: Vitamin D deficiency is associated with more severe PHPT as reflected by PTH levels, but effects on BMD are limited to the cortical 1/3 radius and are quite modest. These data support international guidelines that consider PHPT patients with 25OHD <20 ng/mL to be deficient. However, in this cohort with few profoundly vitamin D-deficient patients, vitamin D status did not appear to significantly impact clinical presentation or bone density.

Context: Vitamin D (25OHD) deficiency may be a modifiable cardiovascular (CV) risk factor. 25OHD insufficiency (20-29 ng/mL) and deficiency (<20 ng/mL) are common in primary hyperparathyroidism (PHPT), but their association with CV disease in PHPT has not been systematically investigated., Objective: This study evaluated whether low 25OHD is associated with subclinical CV disease in PHPT., Design: This is a cross-sectional analysis of PHPT patients with and without low 25OHD., Settings and Participants: We studied 110 PHPT patients in a university hospital setting., Outcome Measures: We measured carotid intima-media thickness; carotid plaque presence/thickness; carotid strain and stiffness; left ventricular mass index; cardiac systolic and diastolic function; and mitral annular calcification., Results: Low 25OHD levels (<30 ng/mL) were observed in 28%, but only 9% had 25OHD deficiency (<20 ng/mL). In the whole group, 25OHD levels negatively correlated with body mass index (r = -0.33, P = .0005), PTH (r = -0.30, P = .001), calcium (r = -0.29, P = .002), renal function, and PHPT duration. CV indices were normal except for carotid intima-media thickness, stiffness, and plaque thickness, which were increased, regardless of 25OHD status. Isovolumic relaxation time was the only CV measure associated with 25OHD (r = -0.26, P = .01). Those with 25OHD less than 20 ng/mL had more severe PHPT and a higher rate of nephrolithiasis. Those with 25OHD less than 30 ng/mL were younger, had higher body mass index, had lower serum phosphate, and were more likely to be male, nonwhite, and Hispanic. Other than lower tissue Doppler e' and higher isovolumic relaxation time within normal range in those with 25OHD less than 30 vs greater than 30 ng/mL, there were no differences in CV indices using either 25OHD threshold., Conclusions: Patients with mild PHPT have subclinical carotid abnormalities, but low 25OHD is not associated with abnormal carotid or cardiac measures. To the extent that PTH levels differentiated those with 25OHD less than 20 but not 30 ng/mL, these data support a 25OHD threshold of 20 ng/mL as clinically relevant in PHPT.