The associations between testosterone and ESA dose may be explained by the fact that testosterone has been shown to suppress hepcidin and increase iron re-utilization. Prior studies have found improved hemoglobin levels when combining ESA and androgen therapy in patients as opposed to ESA alone.

These studies illustrate connections between testosterone levels and several important parameters when treating CKD populations. Although these relationships are most likely not causal, testosterone could be used as a new marker to assess risk and improve treatment. From a nutritional standpoint, testosterone is typically not a direct factor that can be altered, but other lifestyle modifications such as exercise can help dramatically improve testosterone levels.

This factor is of interest to dietitians because improving hormonal profiles can promote more appropriate metabolism of nutrients. Exercise increases the body’s ability to metabolize protein efficiently. This can benefit individuals with a protein-restricted diet. Excessive protein intake may lead to uremia, which can cause protein degradation, metabolic acidosis, inflammation, abnormalities in bone metabolism, insulin resistance as well as other hormonal changes, secondary hyperparathyroidism, electrolyte imbalances, neuropathy, uremic toxins (J Ren Nutr 2007;17:84-87).

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Studies have shown that exercise is a powerful contributor in stimulating anabolic hormones, muscle mass, and strength gains beyond that of pharmaceutical hormonal injections of anabolic agents alone, and this has been demonstrated in a cohort of CKD patients (J Am Soc Nephrol 2006;17:2307-2314).

Previous studies have also demonstrated that exercise programs in combination with low protein diets in non-dialysis CKD patients are associated with more profound improvements in muscle mass, strength, physical function, nutritional status, CRP, and interleukin-6 when compared with low protein diets alone. This particular information is noteworthy because many clinicians still avoid protein restrictions for fear of inducing protein-energy wasting.

The addition of exercise to improve the efficacy of low protein diets may offer a more comprehensive lifestyle modification option for CKD patients that more clinicians may trust. At this time, exercise interventions in CKD populations typically improve many of the more classic outcome measures.

Additional research may help elucidate whether testosterone levels in men could indicate whether exercise interventions should be promoted. Because dietitians are necessary in promoting more lifestyle modifications in patients, they may need to become more proactive when convincing CKD patients, especially those aged 29-69, to engage in regular exercise programs.