From the Guidelines
Testosterone supplementation is not recommended as a means to increase glomerular filtration rate (GFR) due to the lack of direct evidence supporting its effectiveness in improving renal function in the context of gender-affirming hormone therapy (GAHT) 1.
Key Considerations
- The current evidence suggests that GAHT can result in alterations in body mass index, muscle mass, and fat mass, which may ultimately reflect changes in body composition, volume of distribution, and the generation of creatinine 1.
- Estimates suggest that a transgender person on testosterone for at least 1 year manifests a nearly 4‐kg increase in lean body mass 1.
- The use of cystatin C is proposed as a framework to evaluate kidney function in transgender individuals, as it is less dependent on both muscle mass and dietary intake 1.
- If cystatin C is unavailable, recent common practice is to use the creatinine reference range and to calculate creatinine clearance based on one's affirmed gender 1.
Clinical Implications
- Clinicians should be aware of the potential changes in laboratory values, including renal function, in patients undergoing GAHT 1.
- The duration of GAHT, the dose, and the route of administration should be recorded, and laboratory values should be interpreted in the context of GAHT 1.
- For those on GAHT for more than 1 year, many laboratory values should be interpreted based on their affirmed gender 1.
- The potential risks and benefits of testosterone supplementation should be carefully considered, and patients should undergo comprehensive evaluation and regular monitoring 1.
From the Research
Testosterone Supplementation and GFR
- The relationship between testosterone supplementation and glomerular filtration rate (GFR) is complex and not fully understood 2, 3, 4, 5.
- Some studies suggest that low testosterone levels may be associated with a higher risk of chronic kidney disease (CKD) and mortality in men with CKD 2, 3, 4.
- However, the evidence on whether testosterone supplementation can increase GFR or improve kidney function is limited and inconclusive 3, 5.
- One study found that higher log testosterone was associated with significantly lower mortality in men with CKD, but the effect of testosterone supplementation on GFR was not directly assessed 2.
- Another study suggested that low testosterone may increase the risk of CKD in the general population and the risk of all-cause mortality and cardiovascular events in men with CKD, but the potential benefits of testosterone supplementation on GFR were not evaluated 3.
- A prospective population-based study found that men with low testosterone levels had a higher hazard ratio of developing CKD compared to those with normal levels, but the study did not investigate the effect of testosterone supplementation on GFR 4.
- A review of clinical and experimental studies on the impact of testosterone on CKD progression and prognosis found that the evidence is controversial and that more research is needed to determine the potential benefits and risks of testosterone supplementation on GFR 5.
- A study on testosterone supplementation modes and their effects on serum testosterone levels found that transdermal testosterone patches and hydroalcoholic gel can effectively restore normal hormonal values and correct signs and symptoms of hypogonadism, but the study did not assess the effect of testosterone supplementation on GFR 6.