Prevalence and Predictors of Renal Calcification in Primary Hyperparathyroidism

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Serum phosphate and CaP-product levels were significantly higher in patients with nephrocalcinosis compared with patients with nephrolithiasis.
Serum phosphate and CaP-product levels were significantly higher in patients with nephrocalcinosis compared with patients with nephrolithiasis.

Higher serum parathyroid hormone (PTH) and calcium levels were associated with renal calcifications in patients with primary hyperparathyroidism (PHPT), which is dependent on the severity of their condition, according to a study published in The Journal of Endocrinology & Metabolism.

While it is understood that primary hyperparathyroidism is often associated with renal calcification, few studies have evaluated the prevalence and potential biochemical predictors of renal calcification. Thus, researchers conducted a nested case-control study in which 617 patients (median age, 63) with PHPT underwent a computed tomography (CT) scan of the kidneys and urinary tract to assess the incidence of nephrolithiasis and nephrocalcinosis and reveal any biochemical predictors.

CT scans exposed renal calcifications in 144 patients (23%); 7 had both nephrolithiasis and nephrocalcinosis, 76 had nephrolithiasis, and 75 had nephrocalcinosis. Nephrolithiasis was unilateral in 68% and bilateral in 32% of cases; nephrocalcinosis was unilateral in 65% and bilateral in 35% of cases.

Compared with patients who had nephrolithiasis, body height, weight, and body mass index (BMI) were significantly lower in patients who had nephrocalcinosis (P <.05).  In addition, patients with nephrolithiasis were significantly more likely to have hypercalciuria (P <.01).

With regard to biologic predictors, compared with patients who did not have renal calcifications, patients who did were found to have significantly higher levels of ionized calcium, parathyroid hormone, and 24-h calcium excretion (P <.01 for all). In addition, patients with nephrocalcinosis had higher plasma levels of phosphate and a higher calcium-phosphate product than patients with nephrolithiasis (P <.05 for both).

As a secondary outcome, 12% of the total population exhibited impaired renal function, but researchers found no difference in renal function between patients with and without renal calcification.

Researchers cited a lack of a control group as one of several study limitations. This, in particular, hindered their ability to compare the prevalence of renal calcification and impaired renal function in a background population.

“Higher levels of calcium and PTH were associated with renal calcifications,” the researchers said, continuing, “which supports the notion that severity of the disease is of importance to the development of nephrolithiasis and nephrocalcinosis.”

Reference

Ejlsmark-Svensson H, Bislev LS, Rolighed L, Sikjær T, Rejnmark L. Predictors of renal function and calcifications in primary hyperparathyroidism [published online June 27, 2018]. J Endocrinol Metab. doi:10.1210/jc.2018-00923

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