Background: The impairment of renal function can affect the clinical presentation of primary hyperparathyroidism (PHPT) increasing cardiovascular morbidity, fracture rate and the risk of mortality.

Aim: To study the differences in bone status in a series of consecutive patients affected by PHPT without overt renal failure at diagnosis grouped according to creatinine clearance (C_cr).

Methods: 161 consecutive patients with PHPT were studied. They were divided in two groups based on C_cr. Group A had C_cr 70 ml/min (n = 49) and group B had C_cr > 70 ml/min (n = 112). PTH, total and ionized serum calcium, urinary calcium and phosphate, serum 25(OH)D3, serum and urinary bone markers, lumbar, forearm and femoral BMD were evaluated.

Results: Patients in group A were older than those in group B (P < 0.0001). PTH levels did not differ in the two groups while both urinary calcium and phosphorous were lower in group A than group B (P < 0.01). Lower BMD was evident in group A at lumbar spine (P < 0.002), forearm (P < 0.0001) and femur (P < 0.01). In asymptomatic PHPT (aPHPT), those with C_cr 70 ml/min had lower forearm BMD than patients with higher C_cr (P < 0.00001). When adjusting for age and BMI, in PHPT BMD at each site persisted being lower (P < 0.05) in group A than group B. In all PHPT subjects, Ccr ( =0.29, P < 0.0005), age ( 0.27, P < 0.00001) and PTH levels ( 0.27, P < 0.0005) were all independently associated with forearm BMD.

Conclusions: In PHPT a slight decrease in renal function is associated with more severe BMD decrease, independently of age, BMI and PTH levels. This association is also present in aPHPT and strengthens the NIH recommendations for surgery in patients with mild PHPT.