A very interesting article in this month's JASN by Herlitz et al describes a cohort of 10 bodybuilders with chronic kidney disease, making a compelling case that anabolic steroid use is an underrecognized cause of secondary FSGS. The paper is strengthened by the fact that nine of the patients underwent renal biopsy documenting surprisingly aggressive forms of FSGS in many of these patients, including some with the "collapsing" variant of FSGS and others with surprisingly high degrees of interstitial fibrosis and tubular atrophy which are not characteristially seen with secondary FSGS. Perhaps even more convincingly for providing a link between bodybuilding and secondary FSGS, the authors describe a patient whose serum creatinine and proteinuria IMPROVE once the patient's intensive steroid/exercise regimen stops, then gets worse when he returns to this regimen against the advice of his physicians.
There are other health problems already associated with anabolic steroid use--these include gynecomastia, dyslipidemia, testicular atrophy, decreased fertility rates, some forms of hepatotoxicity, neuropsychiatric disorders, and developing a massively enlarged head a la disgraced baseball player Barry Bonds. It seems as if kidney disease can now be added to the list.
As a caveat, however, the authors also point out that there are potential other explanations for how bodybuilding might be linked to FSGS. These individuals were typically on regimens consisting of complicated cocktails of steroids, growth hormone, insulin, protein shakes, diuretics, and other supplements whose content is not carefully regulated. Therefore it remains possible that a substance other than anabolic steroids is the common nephrotoxin amongst these individuals. Furthermore, it's already known that elevated BMI in obese patients can result in secondary FSGS; perhaps their increased lean body mass itself drives the process. High protein diets may expose podocytes to unusually high serum protein levels; could this contribute to toxicity?
One final tidbit I learned from this article: individuals who take creatine supplements (another baseball reference: this is one of the few substances that home run guru Mark McGwire has admitted to taking) may have a falsely-elevated serum creatinine based on the fact that creatine is coverted to creatinine. This limitation can be overcome by measuring a full creatinine clearance in which a 24-hour urine creatinine and simultaneous serum creatinine are used.