Cystatin C-Based eGFR Changes during Gender-Affirming Hormone Therapy in Transgender Individuals

Laboratory Monitoring in Transgender and Gender-Diverse Individuals

BACKGROUND

Increasing numbers of transgender and gender-diverse individuals are seeking initiation of gender-affirming hormone therapy. This aligns an individual's physical characteristics with their gender identity and improves psychological outcomes. Physical changes, including changes to muscle mass and body fat redistribution, can alter sex-specific laboratory reference ranges.

CONTENT

We review the impact of gender-affirming hormone therapy on laboratory parameters with sex-specific reference ranges, with a focus on hemoglobin/hematocrit, renal function, cardiac biomarkers, and prostate-specific antigen.

SUMMARY

Gender-affirming hormone therapy results in changes in laboratory parameters with sex-specific reference ranges. For individuals established on gender-affirming hormone therapy, reference ranges that align with an individual's gender identity should be used for hemoglobin/hematocrit, serum creatinine, and high-sensitivity cardiac troponin and N-terminal brain natriuretic peptide. Clinicians should interpret these biomarkers according to the reference range that aligns with one's affirmed gender.

Association between estrogen and kidney function: population based evidence and mutual bidirectional Mendelian randomization study

BACKGROUND

Previous studies have suggested a potential role of estrogen in the pathophysiology of chronic kidney disease (CKD); however, the association and causality between estrogen and kidney function remain unclear.

METHODS

The cross-sectional correlation between serum estradiol concentration and estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (ACR) was analyzed using data from the National Health and Nutrition Examination Survey 2013-2016. Causality was tested using mutual bidirectional Mendelian randomization (MR) approaches based on six large-scale GWAS studies. Weighted generalized multivariate linear regression was employed to estimate the association between estradiol and eGFR and ACR, and a restricted cubic spline analysis was utilized to investigate potential nonlinear relationships.

RESULTS

A total of 8932 participants were included. Serum estradiol concentration was positively associated with eGFR after adjusting for potential covariates (β, 0.76; 95% CI 0.24 to 1.27) and with ACR (β, 5.99; 95% CI 1.62 to 10.36). A nonlinear positive association was found between estradiol and eGFR, while an inverse "V"-shaped relationship was seen with ACR. Sensitivity analyses confirmed the stability of the relationship between estradiol and eGFR but indicated a less robust association with ACR. Stratified analysis showed that the association between estradiol and eGFR was particularly significant in populations with CKD and hypertension. All forward MR analyses demonstrated a positive causal relationship between estradiol and eGFR, but no causality was found between estradiol and ACR. No reverse causal association was observed.

CONCLUSIONS

Serum estradiol concentration was causally associated with eGFR. Further longitudinal research is needed to validate these findings.

Embedding Equity and Inclusion Principles Into Nephrology Board Examinations: An Essential Part of Our Path Toward Kidney Health Justice

Recognition of widespread health inequalities across disease conditions and their startling impact on morbidity and health care costs have motivated multiple professional societies to ensure board examinations reflect and enhance inclusive, anti-biased, and equitable care. In this perspective, we offer five nephrology case examples and accompanying learning objectives to demonstrate how principles of inclusion, equity, and anti-bias can be embedded into nephrology examinations to enhance care for all populations.

Embracing sex-specific differences in engineered kidney models for enhanced biological understanding of kidney function

In vitro models serve as indispensable tools for advancing our understanding of biological processes, elucidating disease mechanisms, and establishing screening platforms for drug discovery. Kidneys play an instrumental role in the transport and elimination of drugs and toxins. Nevertheless, despite the well-documented inter-individual variability in kidney function and the multifaceted nature of renal diseases-spanning from their origin, trigger and which segment of the kidney is affected-to presentation, progression and prognosis, few studies take into consideration the variable of sex. Notably, the inherent disparities between female and male biology warrants a more comprehensive representation within in vitro models of the kidney. The omission of sex as a fundamental biological variable carries the substantial risk of overlooking sex-specific mechanisms implicated in health and disease, along with potential differences in drug responsiveness and toxicity profiles between sexes. This review emphasizes the importance of incorporating cellular, biological and functional sex-specific features of renal activity in health and disease in in vitro models. For that, we thoroughly document renal sex-specific features and propose a strategic experimental framework to integrate sex-based differences into human kidney in vitro models by outlining critical design criteria to elucidate sex-based features at cellular and tissue levels. The goal is to enhance the accuracy of models to unravel renal mechanisms, and improve our understanding of their impact on drug efficacy and safety profiles, paving the way for a more comprehensive understanding of patient-specific treatment modalities.

Cystatin C is associated with osteoporosis and fractures: An observational study based on Mendelian randomization analysis

OBJECTIVES

Osteoporosis is characterized by decreased bone mass and damaged bone microstructure, often leading to fragility fractures. Low bone mineral density is a key risk factor for fractures. Serum cystatin C (CysC), an endogenous marker of glomerular filtration rate, is negatively correlated with bone mineral density and may be a potential risk factor for osteoporosis. This study aims to investigate the association and potential pathogenic mechanisms between CysC and osteoporosis and fractures in the general population by combining cohort analysis and Mendelian randomization (MR) analysis.

METHODS

Large-scale prospective cohort data from the UK Biobank and summary statistics from genome-wide association study (GWAS) in European populations were utilized, with strict exclusion criteria applied (excluding non-white individuals, those with thyroid diseases, gastrointestinal dysfunction, kidney diseases, rheumatoid diseases, malignant tumors, chronic infections or inflammatory diseases, diabetes, hypertension, and individuals taking medications that affect bone metabolism). Multivariable linear regression, logistic regression, and Cox proportional hazards models were used to analyze the relationship between CysC and bone mineral density, osteoporosis, and fracture risk. All analyses were performed using three sequential models to adjust for confounding factors: Model 1 adjusted for demographic characteristics and lifestyle factors; Model 2 further adjusted for renal function based on Model 1; and Model 3 further adjusted for physical activity based on Model 2. Restricted cubic spline models were used to explore non-linear relationships, and MR analysis was conducted to assess the causal associations between CysC and osteoporosis and fractures.

RESULTS

Multivariate analysis showed that after adjusting for basic variables (Model 1), there was no correlation between CysC and estimated bone mineral density (eBMD) in the overall study population; however, when stratified by gender, both males and females exhibited a significant negative correlation (P<0.001). After further adjustment for renal function (Model 2) and physical activity level (Model 3), CysC became negatively correlated with eBMD in the overall population (P<0.001). Moreover, multivariable logistic regression consistently demonstrated that CysC concentration was significantly positively associated with osteoporosis risk (P<0.01), and this association remained stable across all models. In all populations and models, multivariate Cox regression analysis indicated that subjects in the highest quartile (Q4) of CysC had a significantly increased risk of developing osteoporosis (P<0.001). In the overall population, the positive association between Q4 CysC levels and fractures was observed only in Models 2 and 3, with a hazard ratio of 1.118 (both P<0.001); however, after gender stratification, this association disappeared in males (P>0.05). Additionally, restricted cubic spline regression analyses revealed a significant non-linear relationship between CysC and the incidence of osteoporosis and fractures (P<0.05). MR analysis, using 167 single nucleotide polymorphisms (SNPs) as instrumental variables, showed no direct causal relationship between CysC and osteoporosis or fractures (P≥0.05), a finding that differs from previous studies in special populations.

CONCLUSIONS

Elevated levels of CysC are significantly associated with an increased risk of osteoporosis and fractures, and this association is more pronounced in females. Renal function and physical activity levels may be important factors influencing this relationship. The link between CysC and osteoporosis and fractures may be mediated by several mechanisms: Eelevated CysC may lead to abnormalities in vitamin D and mineral metabolism, thereby inhibiting bone formation; renal dysfunction may exacerbate inflammation, affecting bone resorption; or in the osteoporosis state, increased osteoclast differentiation may result in elevated CysC levels. These findings support the potential use of CysC as a biomarker for predicting the risk of osteoporosis.