| Summary: | Background: Metabolic syndrome (MS) affects approximately one quarter of the world, making it a global epidemic (1). Although MS has been associated with increased risk of rapid decline in the glomerular filtration rate (GFR) (2), only a few studies have investigated the association of MS with abnormally elevated GFR, known as renal hyperfiltration (RHF). Previous studies of MS and RHF were limited by the use of estimated GFR (eGFR) and the results were divergent. Establishing the relationship between MS and RHF is of clinical importance as there are promising treatment options for RHF. Methods: In the Renal Iohexol Clearance Survey (RENIS) we included 1551 subjects from the population based Tromsø survey (2007-2009). The participants were 50-62 years old without known diabetes, cardiovascular disease or kidney disease. The GFR was measured (mGFR) using iohexol clearance. The aim was to investigate the relationship between MS and RHF. The dichotomous variable for RHF was defined as an absolute GFR (ml/min) above the 90th percentile adjusted for gender, age and height (3). Results: MS was associated with increased absolute GFR (ml/min) and RHF (yes/no) independent of age, sex and height (OR 2.44 95% CI; 1.71 – 3.46, p<0.001). All risk factors except for hypertension were independently associated with RHF and increased absolute GFR. The risk of RHF was highest in subjects fulfilling 5 out of 5 criteria (OR 4.06, 95% CI; 1.54-10.67, p=0.005) compared to those fulfilling 0 or 1 criteria. Conversely, MS was not associated with higher estimated GFR based on creatinine, cystatin C or both together. Conclusions: Subjects with MS have a higher absolute GFR and increased risk of RHF compared to subjects without MS. RCTs are needed to explore whether treatment of RHF can prevent accelerated GFR decline and CKD in persons with MS.
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