INTRODUCTION:

Testosterone, produced in the testicles, is crucial for maintaining bone density, fat distribution, muscle strength and mass, and the production of red blood cells¹. It also regulates secondary male characteristics², has anabolic effects, promotes skeletal muscle growth, and stimulates erythropoiesis, resulting in higher hematocrit levels in men compared to women³.

Testosterone production can decline due to aging, medications, certain health conditions, and genetic disorders⁴. Older men may experience late-onset hypogonadism (LOH), characterized by symptoms such as reduced virility, fatigue, and muscle loss⁵. Similar symptoms can occur in advanced chronic kidney disease, regardless of testosterone levels^6.7.

Recent studies have begun to unravel the complex relationships between testosterone levels and other critical biomarkers, such as urea, creatinine, hemoglobin⁸, and red blood cell properties. Understanding these relationships is vital for developing comprehensive health strategies and improving clinical outcomes in men^9,10

Hemoglobin, the protein in red blood cells that carries oxygen throughout the body, is another critical marker of health¹¹. Its levels can reflect not only oxygen transport capacity but also overall blood health and nutritional status^12,13. The properties of red blood cells—such as their size, shape, and concentration—further contribute to understanding an individual’s hematological profile¹⁴.

High testosterone levels can lead to secondary erythrocytosis, causing symptoms of hyperviscosity such as headaches, fatigue, blurred vision, and paresthesias¹⁵. For patients with elevated hematocrit levels over 54%, discontinuation of testosterone therapy should be considered, along with phlebotomy. Elevated testosterone may also stimulate the growth of prostate cancer in men^16,17. Conversely, low testosterone is associated with depression, reduced self-esteem, sleep disturbances, increased body fat, and fatigue¹⁸.

Obesity increases the activity of an enzyme called aromatase in fat tissue, which converts testosterone into estradio¹⁹. This conversion plays a significant role in regulating body fat and can further reduce testosterone production by creating a negative feedback effect on the hypothalamic-pituitary-gonadal axis²⁰. On the other hand, low testosterone levels can lead to increased accumulation of visceral body fat, which raises insulin resistance²¹.

Genetically predicted testosterone levels are linked to chronic kidney disease (CKD) and poorer kidney function in men; however, kidney function itself does not affect testosterone levels. Biochemical evidence indicates that testosterone is involved in promoting glucose utilization by stimulating glucose uptake, glycolysis, and mitochondrial oxidative phosphorylation²². Additionally, testosterone is linked to muscle growth in men by stimulating the hormone erythropoietin, which increases blood hemoglobin levels and red blood cell size²³.

Most experiments on this topic have been conducted on animals using testosterone injections as treatment²⁴.

OBJECTIVE:

The purpose of this study was to determine whether there is a correlation between testosterone levels in males who do not suffer from chronic kidney disease and various red blood cell properties, including hemoglobin (Hg in g/dL), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), hematocrit (HCT), mean corpuscular hemoglobin concentration (MCHC in h/dL), and red cell distribution width (RDW)

MATERIALS AND METHODS:

Participants:

A total of 100 participants aged 24 to 74 years were included in the study. Participants were allocated into two age groups: Group 1 consisted of individuals aged less than 65 years, while Group 2 included individuals aged 65 years and older.

This study was approved by the Al-Hawash Private University Ethics Committee with approval number 002-2024. All participants gave their written consent to take part in the study after being informed in details about the nature and objective of the study.

Inclusion and Exclusion Criteria:

Participants were included in the study if they: were healthy men with no known chronic illnesses or conditions that could affect testosterone levels or renal function (such as diabetes, hypertension, or cardiovascular diseases), have normal renal function (indicated by serum creatinine levels within the normal range (generally <1.2mg/dL) and urea levels that do not indicate renal impairment) and have normal hemoglobin levels (typically between 13.5 to 17.5g/dL for men) and red blood cell counts within the standard range to rule out any underlying hematological disorders.

On the contrary, participants were excluded if they: had chronic illnesses such as kidney disease, liver disease, or endocrine disorders, are currently taking medications that could influence testosterone levels (such as anabolic steroids, testosterone replacement therapy, or certain hormonal medications) within the last six months, had a history of prostate cancer or any prostatic disorders and had any known blood disorders such as anemia.

Sample Collection and Laboratory Analysis:

Blood samples were collected from all participants for laboratory analysis. Testosterone levels were measured using the Roche Cobas e411 device. Urea and creatinine levels were calibrated using the Roche Cobas C 311 device. Hemoglobin and red blood cell properties, including mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), hematocrit (HCT), mean corpuscular hemoglobin concentration (MCHC), and red cell distribution width (RDW), were assessed using the Sysmex XN-330 analyzer.

Laboratory Setting:

All parameters were measured at the Al Hawash Private University Hospital (Dr. Farzat Ayoub Hospital), ensuring that all laboratory procedures adhered to standard operating protocols for accuracy and reliability.

Statistical Analysis:

Statistical analyses were conducted using the SPSS version 24 software. The normality of the data was assessed using the Kolmogorov–Smirnov test. Statistical significance was set at a p-value of <0.05 and descriptive statistics, including means and standard deviations, were calculated for all measured parameters. Independent t-test was used for comparisons between the two groups for all the studies variables. Pearson correlation was used to assess the correlation between testosterone levels and the studies parameters.

RESULTS:

The t-test for two independent samples revealed significant differences in the average levels of testosterone, hemoglobin (HGB), and mean corpuscular hemoglobin concentration (MCHC) between the two groups. Males under 60 years of age exhibited higher levels of these parameters compared to their counterparts aged 60 years and older.

Statistical Analysis of Parameters:

The results indicate statistically significant differences between the means of the parameters, including urea, red cell distribution width-standard deviation (RDW-SD), and red cell distribution width-coefficient of variation (RDW-CV), between Group 1 and Group 2.

Table (1) demonstrates that there are no statistically significant differences (P>0.005) between the means of creatinine, red blood cells (RBCs) per million/mm³, hematocrit percentage (HCT %), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) between the studied groups.

Correlation Analysis:

The correlation between testosterone and urea was found to be statistically insignificant, as illustrated in Figures 1 and 2. However, there was a statistically significant correlation between testosterone and other variables. Specifically, a p-value of less than 0.05 indicates a statistically significant inverse correlation between testosterone levels and each of the following variables: age, creatinine, RBC count, MCV, MCH, and RDW-SD.

Age-Related Changes in Testosterone Levels:

Testosterone levels significantly decreased with age (p < 0.05), as shown in Figure 3. The linear regression model for this relationship is expressed as: Testosterone = 6.94 - 0.03 × Age

Impact of Testosterone on Other Parameters:

Creatinine: Creatinine levels significantly increased at lower testosterone levels (p<0.05), as depicted in Figure 4. The predictive linear model is: Creatinine = 1.22 - 0.04 × Testosterone

RBC Count: RBC levels significantly decreased at lower testosterone levels (p<0.05), illustrated in Figure 5. The predictive model is: RBC × 10^6/mm³ = 4.28 + 0.14 × Testosterone

MCV: MCV significantly decreased at lower testosterone levels (p<0.05), as shown in Figure 6. The predictive model is: MCV = 102 - 2.73 × Testosterone

MCH: MCH significantly decreased at lower testosterone levels (p < 0.05), represented in Figure 7. The predictive model is: MCH pg = 33.24 - 0.83 × Testosterone

RDW-SD: RDW-SD significantly decreased at lower testosterone levels (p<0.05), as illustrated in Figure 8. The predictive model is: RDW-SD = 53.6 - 1.75 × Testosterone

Table 1: Results of t-test for two independent samples .*P value ≤0.005

Parameters	˂60 years group1 (n=12)	≥60 years group2 (n=88)	p-value
Testosterone	6.4 ± 0.77	4.99 ± 1.21	0.000*
Createnine mg/dl	0.97 ± 0.15	1.04 ± 0.14	0.088
Urea mg/dl	17.67 ± 2.61	26.67 ± 5.66	0.000*
RBC ×10⁶/mm³	4.96 ± 0.58	5.03 ± 0.69	0.718
HGB g/dl	15.13 ± 0.26	14.31 ± 0.93	0.000*
HCT %	43.53 ± 0.6	43.75 ± 2.66	0.959
MCV	87.78 ± 4.93	87.93 ± 9.85	0.516
MCH pg	30.47 ± 3.27	28.77 ± 3.96	0.159
MCHC h/dl	34.7 ± 0.97	32.66 ± 1.51	0.000*
RDW-SD	40.12 ± 3.48	45.2 ± 6.33	0.008
RDW-CV	12.57 ± 0.76	14.06 ± 1.72	0.004*

Figure1: The relationship between the value of parameters (HGB, MCT, MCV, MCH) in the two studied groups

Figure2: The relationship between the value of parameters (Urea, MCHC, RDW) in the two studied groups

Table 2: the correlation between testosterone and Createnine, Urea, RBC, HGB, HCT, MCV, MVH, MCHC, RDW^* pvalue≤ 0.05

	Pearson correlation (r)	p-value
Testosterone	-	-
Age	-0.353^**	0.000^**
Createnine mg/dl	-0.312^**	0.002^*
Urea mg/dl	0.113	0.261
RBC ×10⁶/mm³	0.266^**	0.007
HGB g/dl	0.154	0.126
HCT %	0.073	0.473
MCV	-0.364^**	0.000^**
MCH pg	-0.264^**	0.008
MCHC h/dl	0.132	0.191
RDW-SD	-0.347^**	0.000^**
RDW-CV	0.035	0.727

Figure 3: The relationship between age and testosterone:

Figure 4: The relationship between testosterone and Creatinine :

Figure 5: The relationship between testosterone and RBC :

Figure 6: The relationship between testosterone and MCV

Figure 7: The relationship between testosterone and MCH

Figure 8: The relationship between testosterone and RDW-SD.

DISCUSSION:

Age-Related Decline in Testosterone:

The decline of testosterone levels with age is a well-established phenomenon. Studies indicate that testosterone production decreases by about 1% per year after the age of 30. This gradual decline can lead to various health issues in older men, including fatigue, reduced libido, and diminished muscle mass . Our findings align with this literature, demonstrating significantly lower testosterone levels in older participants compared to younger counterparts.

Impact on Red Blood Cell Properties:

Testosterone plays a crucial role in erythropoiesis—the production of red blood cells—by stimulating erythropoietin production. Our study found that lower testosterone concentrations were associated with decreased hemoglobin levels and other red blood cell parameters. This relationship is significant as anemia can severely impact the quality of life among older adults¹⁵.

Clinical Implications of Testosterone Therapy:

The implications of our findings suggest that monitoring testosterone levels in aging men is essential for identifying those at risk for anemia and other related health issues. Testosterone replacement therapy may offer benefits for men experiencing symptoms related to low testosterone; however, it must be approached cautiously due to potential risks associated with therapy, including cardiovascular events and prostate health concerns.

Influence of Urea and Creatinine Levels:

In our study, increased creatinine levels were observed alongside lower testosterone concentrations. This relationship may suggest that declining kidney function could be linked to hormonal imbalances in aging men . Elevated urea and creatinine can indicate renal impairment, which is common in older populations. Therefore, clinicians should consider kidney function when assessing testosterone levels and related health outcomes.

CONCLUSION:

This clinical study highlights the significant relationship between testosterone levels and various biological markers such as urea, creatinine, hemoglobin, and red blood cell properties in healthy men from Syria. The findings underscore the importance of regular monitoring of testosterone levels as men age to identify potential health risks early on. Future research should focus on longitudinal studies to further elucidate these relationships and explore the therapeutic potential of testosterone replacement therapy while considering individual patient factors.

By understanding these dynamics better, healthcare providers can develop more effective strategies for managing men's health as they age, ultimately improving their quality of life.

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Received on 29.09.2024 Revised on 22.12.2024

Accepted on 03.02.2025 Published on 12.06.2025

Available online from June 14, 2025

Research J. Pharmacy and Technology. 2025;18(6):2848-2852.

DOI: 10.52711/0974-360X.2025.00409

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