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Renal calcifications associated with disease severity in primary hyperparathyroidism
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Patients with primary hyperparathyroidism have a high prevalence of renal calcifications that are typically linked to the severity of the disease, according to findings published in The Journal of Clinical Endocrinology & Metabolism.
In a nested case-control study, Henriette Ejlsmark-Svensson, a doctoral student and fellow in the department of clinical medicine at Aarhus University Hospital, Denmark, and colleagues assessed 792 patients diagnosed with primary hyperparathyroidism between 2005 and 2015 at Aarhus University Hospital through the Danish National Patient Register (mean age, 63 years; 77% women; 99% white). Researchers analyzed the prevalence of renal calcifications in the cohort, defined as nephrolithiasis or nephrocalcinosis, as evaluated by routine CT scan at diagnosis.
Within the cohort, 617 underwent a CT scan. Of those, 144 (23%) had renal calcifications identified, including 76 (53%) with nephrolithiasis and 75 (52%) with nephrocalcinosis and seven (5%) with both nephrolithiasis and nephrocalcinosis.
Among patients with nephrolithiasis, 52 (68%) were cases of unilateral nephrolithiasis and 24 (32%) had bilateral nephrolithiasis. Among patients with nephrocalcinosis, 49 (65%) had unilateral nephrocalcinosis and 26 (35%) had bilateral nephrocalcinosis, according to the researchers.
Patients with and without renal calcifications did not differ in age or sex, but patients with renal calcifications had a slightly lower BMI vs. those without calcifications, as well as increased levels of 24-hour urinary calcium and calcium ions (Ca2+). Plasma phosphate levels were significantly lower in patients with calcifications. Additionally, patients with nephrocalcinosis had lower height, weight and BMI vs. patients with nephrolithiasis (P < .05). Moreover, patients with nephrocalcinosis had significantly higher levels of plasma phosphate and the calcium-phosphate product vs. those with nephrolithiasis. Hypercalciuria was present in 67% of patients with nephrolithiasis and 49% of patients without nephrolithiasis had hypercalciuria.
The use of 24-hour urinary calcium as a predictor of nephrolithiasis was found to have poor diagnostic accuracy, with an area under the curve below 0.6 (95% CI, 0.53-0.67), according to researchers.
In an analysis in which Ca2+ levels were classified into tertiles, the researchers found that increases in renal calcifications were positively correlated with increased levels of Ca2+ (P for trend < .001). Researchers also observed a higher rate of renal calcifications (33.5%) in patients with moderate to severe hypercalcemia (defined as 1.47 mmol/L or higher) vs. patients with mild to moderate hypercalcemia (20.6%; P < .01) or mild hypercalcemia (15.9%; P < .001). However, there was no difference in renal calcifications observed between patients with mild and mild to moderate hypercalcemia (P= .22). In an analysis stratifying parathyroid hormone (PTH) levels by tertiles, researchers found the rate of renal calcifications was 17% in those with a PTH less than 9 pmol/L, 23% in patients with PTH between 9 pmol/L and 12.8 pmol/L, and 30% in patients with PTH of at least 12.8 pmol/L (P for trend < .01).
Logistic regression analyses revealed an increase in risk for any renal calcifications and risk for nephrolithiasis in the highest vs. the lowest tertiles of PTH and Ca2+ levels, whereas risk for nephrocalcinosis was elevated only in the lowest vs. highest tertiles of Ca2+, according to researchers. Adjusted analyses revealed that only high levels of Ca2+ were correlated with risk for any renal calcifications (OR = 1.922; 95% CI, 1.065-3.469).
“We found an overall prevalence of renal calcifications of 23% in patients with [primary hyperparathyroidism],” the researchers wrote. “Higher levels of calcium and PTH were associated with renal calcifications, which supports the notion that severity of the disease is of importance to the development of nephrolithiasis and nephrocalcinosis. “In [primary hyperparathyroidism], a high 24-hour renal excretion of calcium was associated with renal calcifications, which supports the hypothesis of hypercalciuria being of importance.” – by Jennifer Byrne
Disclosures: The authors report no relevant financial disclosures.
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