Experts agree that anabolic steroids damage virtually every organ in the body. Recent studies show that the kidneys are on set of organs that come under particularly harmful attack.
Anabolic steroids may help athletes gain muscle mass and strength, but this bulking up comes at the risk of serious kidney damage, according to research published in the Journal of the American Society of Nephrology. The findings indicate that the habitual use of anabolic steroids has potential harmful effects on the kidneys that were not previously recognized.
“Anabolic steroid abuse is prevalent among both amateur and professional athletes. While these drugs are known to cause endocrine and liver dysfunction, until now their effects on the kidneys have not been appreciated,” says Vivette D’Agati, M.D., the Columbia University Medical Center researcher and practicing physician who led the study. Dr. D’Agati and her colleagues recently conducted the study, the first of its kind to identify kidney disease following long-term abuse of anabolic steroids.
The investigators studied a group of 10 bodybuilders who took anabolic steroids for years. All developed protein leakage into the urine and severe reductions in kidney function. Kidney biopsies revealed that the bodybuilders had developed a condition called “focal segmental glomerulosclerosis,” a type of scarring within the kidneys. This disease typically occurs when the kidneys are overworked. The kidney damage in the bodybuilders has similarities to that seen in morbidly obese patients, but appears to be even more severe.
When the bodybuilders discontinued steroid use, their kidney abnormalities improved, with the exception of one individual with advanced kidney disease who developed end-stage kidney failure requiring dialysis. The single patient who resumed steroid abuse developed a severe clinical relapse.
The researchers propose that extreme increases in muscle mass drive the kidneys to increase their filtration load, placing harmful levels of stress on these organs. Because the kidney injury following steroid abuse is more severe clinically and pathologically than that seen in morbidly obese patients with even higher body mass indices, it is also likely that anabolic steroids have direct toxic effects on the glomeruli, whose cells bear receptors for these agents.
Aside from increased lean body mass, the cohort of bodybuilders had additional factors that could exert stress on the glomeruli, the million capillary sieves per kidney required for the ultrafiltration of plasma to form urine.
Ingesting massive amounts of protein and other supplements to bulk up, a practice common among heavy weightlifters, appears to cause an increase in renal blood flow and glomerular filtration rate by a variety of mechanisms. While this is an appropriate adaptive response to the increase in nitrogenous waste that is the byproduct of protein metabolism, chronic hyperfiltration from a high-protein diet may accelerate progression to glomerulosclerosis.
Six of the 10 patients also had elevated blood pressure or a history of hypertension at the time of renal biopsy. Systemic hypertension as well as the extreme episodic elevations in blood pressure typically experienced during heavy weight lifting also may contribute to kidney injury.
Because the major laboratory test that measures kidney function, the serum creatinine level, is influenced by the amount of muscle mass a patient has, kidney dysfunction can be difficult to identify in highly muscular athletes.
“Mild increases in creatinine may be overlooked as a normal physiologic response to increased lean body mass. Therefore, more sensitive tests to measure renal function and urinary protein are needed to detect the early stages of kidney disease in this population,” Dr. D’Agati said. “Because young athletes appear healthy and so few admit to use of anabolic steroids, this condition is likely to be under-recognized without more widespread screening of individuals at risk,” she added. “What looks healthy on the outside may be causing silent, progressive injury to the kidneys.”