Urinary calcium excretion and insulin resistance in patients with acromegaly.

Background: Renal complications in acromegaly include glomerular hyperfiltration, insulin resistance, hypercalciuria and urolithiasis. The aim of this study was to investigate whether urinary calcium (U(Ca)) excretion is a direct consequence of growth hormone secretion or secondary to hyperfiltration and/or insulin resistance.
Methods: We performed a cross-sectional study of 58 patients diagnosed with acromegaly. Demographic data were obtained, serum analysis was performed, including insulin-like growth factor (IGF)-1, and 24-h urine collection, to measure urinary protein excretion, U(Ca) and phosphate excretion, as well as fractional excretion of sodium and potassium. We also calculated the homeostasis model assessment of insulin resistance (HOMA-IR).
Results: Patients were predominantly male (60.3%), and their mean age was 45.9 ± 14 years. Hypercalciuria was present in 24% of patients. Patients with higher HOMA-IR had higher IGF-1 levels, a trend toward higher body mass index and higher U(Ca) excretion. In univariate analysis, U(Ca) excretion was associated with HOMA-IR (r = 0.472, P = 0.001), phosphaturia (r = 0.457, P = 0.001), IGF-1 (r = 0.398, P = 0.002) and creatinine clearance (r = 0.394, P = 0.001). HOMA-IR and phosphaturia were independently associated with U(Ca) excretion. No independent associations were found between phosphaturia and HOMA-IR or IGF-1.
Conclusions: The present study revealed an association between hypercalciuria and insulin resistance in patients with acromegaly. Further studies are required to fully understand the pathogenesis of these abnormalities in patients with acromegaly.