The Role of Serum Testosterone as a Lithogenic Factor and Its Correlation with Stone and Urine Composition Amongst Male Stone Formers

ABSTRACT

Introduction: Urolithiasis typically affects adult men more commonly than women with a two- to threefold higher incidence. Stone disease has been found to have an inverse relationship as one ages. This gender and age differentiation invites the role of testosterone as a possible lithogenic factor. Our study aims at determining the role of testosterone as lithogenic factor and its relation to urinary and stone components.

Methods: A total of 87 men older than 18 years were enrolled in our study. Early morning free and total testosterone, serum level of the parathyroid hormone, calcium acid, and uric acid were estimated between the 2 groups. Twenty-four hours of urinary oxalate, uric acid, and calcium were estimated in all patients and the control. Stone analysis was done to determine stone composition for stones in the former group.

Results: Of the 87 patients, 48 patients had a history of urolithiasis and 39 patients had no history of urolithiasis. In comparison to non-stone formers, stone formers have higher serum-free and total testosterone, and 24-hour urinary oxalate. A positive and weak-positive correlation was found in relation to 24 hours of urinary oxalate for free and total testosterone, respectively. Calcium oxalate stones were found in 40 patients. Other differences between the 2 groups were not statistically significant.

Conclusions: A higher serum-free and total testosterone, and 24 hours of urinary oxalate were found in male stone formers compared to non-stone formers. Serum testosterone had a positive correlation to urinary oxalate. These findings have a similarity with animal and human studies. A larger prospective study is necessary to establish testosterone as a lithogenic factor in male former-stone patients.


Simanta Jyoti Nath, Debanga Sarma, Puskal K. Bagchi, Sasanka K. Baruah, Rajeev T. Puthenveetil, Saumar J. Baruah

Submitted February 25, 2013 - Accepted for Publication May 12, 2013


KEYWORDS: Serum testosterone, urinary oxalate, calcium oxalate stones

CORRESPONDENCE: Dr. Simanta Jyoti Nath, Department of Urology, Gauhati Medical College & Hospital, Bhangagarh, Guwahati, PIN-78100, Assam, India, ()

CITATION: UroToday Int J. 2013 June;6(3):art 37. http://dx.doi.org/10.3834/uij.1944-5784.2013.06.11

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INTRODUCTION

Urolithiasis affects adult men more commonly than women. The relative frequency of urolithiasis is two- to threefold higher in men than women. Occurrence of idiopathic calcium stones has been reported to be 4 to 5 times higher in men than women [1,2,3]. Stone disease has an inverse relationship with age. The greatest difference in idiopathic calcium oxalate stone formation is seen in the third and fourth decade of life [4]. However, clinical observations have indicated not only a changing frequency and composition of urinary calculi but also a shift in gender and age-related incidences [5]. This gender and age differentiation invites the role of sex hormones as lithogenic factors. In the sixth decade of life, stone incidence, as well as testosterone levels, begin to decline in men [6]. Various experimental animal studies have suggested an association between testosterone and stone disease.

The objective of the study was to determine the possible role of serum testosterone as a lithogenic factor and its relation to urinary and stone components in male stone formers.

Materials and Methods

From February 2011 to November 2012, a total of 87 men older than 18 years were prospectively enrolled in this study that was approved by the institutional ethical committee of Gauhati Medical College & Hospital. Of the subjects, 48 had a history of stones for first time (cases), and 39 persons who attended the urology outpatient department without any history of stones were taken as control. Patients were excluded from the study if they had primary hyperparathyroidism, chronic diarrheal syndromes, intestinal malabsorption, renal tubular acidosis, primary hyperoxaluria, recurrent or active urinary tract infection, primary liver disease, primary gout, ongoing 5-alpha-reductase inhibitor therapy, and debilitating chronic illness.

A serum sample was drawn from each subject between 7 a.m. and 11 a.m. The total and free serum testosterone, serum parathyroid hormone, serum calcium, and serum uric acid were estimated in both cases and control. A 24-hour urine sample was obtained from both the groups and urinary calcium, oxalate, and uric acid were estimated. Stone analysis was done after retrieval in the stone-forming group.

Assays

Free serum testosterone was estimated by radioimmune assays, and total testosterone was estimated by the chemiluminescence method. The 24-hour urinary calcium, uric acid, and oxalate were estimated by Spectrophotometry o-cresolphthalein complexone method, spectrophotometry uricase method, and enzymatic determination.

Statistical Analysis

An independent student t-test was performed to see the difference between the distributions of variables under study for the case and control groups. Pearson correlation tests were done to examine the correlation between serum testosterone (free and total) and 24-hour urinary oxalate. An analysis of variance (ANOVA) test was done to evaluate the differences among age groups in relation to serum testosterone (total and free) for stone formers. Statistical analysis was performed using SPSS (version 16.0) software.

RESULTS

Patients were categorized according to age. Serum total and free testosterone has an inverse relation to age. One way ANOVA test was performed to find out significant changes in testosterone levels in relation to age differentiation. For cases, the P value was estimated to be 0.670 and 0.225 for free and total testosterone, respectively. For the control group it was 0.375 and 0.189 for free and total testosterone, respectively, as shown in Table 1. No significant difference was observed between the different age groups for cases and control.

An independent sample student t-test was done among serum and urine variables. Average free serum testosterone was higher (24.475 vs 18.96 pg/mL, P value = 0.000) in cases in stone formers compared to a healthy volunteer. The average serum total testosterone for cases was 571.37 ng/dl, and for control it was 414.7 ng/dl (normal range: 241 to 827 ng/dl) with a P value of 0.000. From these 2 analyses, it is seen that both free and total testosterone were in a higher range in cases compared to the control group.

The serum level of the parathyroid hormone was estimated between cases and control to find out any variance among stone formers and non-stone formers. The average serum PTH for cases was 37.84 pg/mL, and for control it was 36.3 pg/mL. The P value was estimated to be 0.175, which was not significant on the independent sample test.

Similarly, serum calcium was estimated between both groups. The mean calcium level for cases was 8.67 mg/dl and for control was 8.35 mg/dl. The P value was estimated to be 0.029, which was not significant for both groups.

Serum uric acid was also estimated between the 2 groups. The mean level for cases was 5.22 mg/dl and 5.15 mg/dl for control. An independent sample t-test showed a P value of 0.622, which was not significant for both groups.

In this study, 24 hours of urinary calcium, uric acid, and oxalate levels were estimated between cases and control to find out any significant variance for both groups. For cases, the mean urinary calcium was 182.03 mg/24 hours, uric acid was 461.28 mg /24 hours, and oxalate was 22.93 mg/24 hours. For the control group, the mean urinary calcium was 177.5 mg/24 hours, uric acid was 428.15 mg/24 hours, and oxalate was 14.84 mg/24 hours. On the independent sample t-test, the P value for calcium, uric acid, and oxalate were 0.185, 0.009, and 0.000, respectively. Urinary oxalate for cases was higher compared to the control group, with a significant P value.

The Pearson correlation test was done between 24 hours of the urinary oxalate, serum-free, and total testosterone. For the control group, the total and free testosterone had no positive correlation with urinary oxalate. For cases, the total serum testosterone had a weak positive correlation (P = 0.602) and free testosterone had a positive correlation (P = 0.040), as shown in Table 2. Stone analysis was done after treatment to find out the stone component. In this study, 40 cases (83.3%) had calcium oxalate stones, 6 cases (12.5%) had phosphate stones, and 2 cases (4.16%) had mixed stones.

DISCUSSION

Urolithiasis is a multifactorial disorder influenced by both intrinsic and environmental factors. Among the studied factors, male gender with a 3 times higher incidence of urolithiasis than the female gender is considered a risk factor, but the influence of sex hormones on urinary stone formation remains undetermined. Since the association between serum testosterone and urolithiasis has received only limited attention, the pathogenesis of this male predisposition remains to be elucidated, and thus the reason for this male predominance remains apparently obscure.

Early investigations into the difference in stone formation between sexes noted that men had a higher rate of urinary excretion of oxalate [7], an important promoter of lithogenesis, and women had a higher rate of urinary excretion of citrate [8]. The citrate is an important inhibitor of lithogenesis. Sex hormones are thought to alter oxalate metabolism leading to increased lithogenesis in men. Richardson et al. [9] showed that testosterone can increase the glycolic acid oxidase (GAO) activity by unclear mechanisms, whereas estradiol decreases glycolic acid oxidase activity [3]. GAO is a part of the oxalate-producing pathway. Lee et al. [3] compared the rate of calcium oxalate stone formation of normal male rats, castrated male rats, normal female rats, and castrated female rats fed on a lactogenic ethylene glycol diet. Their observation supports the hypothesis that testosterone plays an important role in the pathogenesis of calcium oxalate stone formation.

Testosterone has an effect on the urinary glycoprotein osteopontin, which is a inhibitor of calcium oxalate crystallization. Yagisawa et al. [10] found that osteopontin expression in the kidney is suppressed in the presence of testosterone and up-regulated by estrogen.

Several studies revealed that the greatest difference in idiopathic stone formation is seen in the third and fourth decades of life [6], and at the sixth decade, the incidence of stones and testosterone begin to decline [2,11]. In the current study, the maximum number of patients was identified between 30 to 39 years of age, and there was no difference among the age groups regarding patient category with relation to total and free serum testosterone. Though the current study failed to establish a relationship between serum testosterone and age, a large cohort study may be necessary to establish any relationship between the two.

Previous animal research has reported a direct correlation between serum testosterone and urinary oxalate excretion. It is generally known that age and sex are risk factors for urolithiasis. Van Aswegen et al. [12] estimated total urinary testosterone concentrations of persons with and without renal stones by means of radioimmunoassay. The total testosterone level of the first morning midstream urine was comparable with 24-hour urine samples of 16 healthy persons (rs = 0.9618). An investigation of the total urinary testosterone confirmed that the concentration is age dependent. A distinct decrease in total testosterone was observed in elderly persons. Therefore the total testosterone concentrations of the 2 groups, with and without stones, were studied within the same age interval (P = 0.8292). The testosterone level differed significantly for the 2 groups (P = 0.0006). In general, the testosterone level of the kidney stone patients was lower than that of their healthy counterparts. In order to determine whether this variation in testosterone concentration would affect the urinary urokinase activity, a correlation study was undertaken. A positive correlation was found between the total urinary testosterone concentrations and the activity of urokinase (rs = 0.7305). It therefore seemed that the total urinary testosterone concentrations may play a role in the pathogenesis of this multifactorial disease, urolithiasis.

A study by Hedayati et al. [14], an estimation of testosterone, free testosterone, estradiol, dihydrotestosterone, and sex hormone binding globulin, revealed hyperandrogenicity among the 8 male stone formers. But they failed to establish a definite relation due to a low number of cases.

Tiselius and colleagues demonstrated no change in urinary oxalate excretion in castrated prostatic carcinoma patients [7]. However, the mean age of these patients was 71 years; little attention was paid to standardizing or quantifying oxalate intake.

In the current study, 24 hours of urinary oxalate was estimated in both cases and the control. The correlation between serum testosterone and urinary oxalate was determined. There was a positive correlation between serum testosterone (total and free) and urinary oxalate. This may prove the hypothetical issue of serum testosterone as a lithogenic factor for calcium oxalate stones in the future. Watson et al. [13] evaluated the effect of serum testosterone on urolithiasis in human models. Although free testosterone was not significantly associated, total testosterone was higher in stone formers in comparison to the control. However, 24 hours of urinary oxalate was not estimated and a definite correlation could not be achieved. Moreover stone analysis was not done to find out the stone component and its probable relation to serum testosterone.

In the current study, both free and total serum testosterone and 24 hours of urinary oxalate are higher and have statistical significant values (free testosterone: P = 0.00, total testosterone: P = 0.00, 24 hours of urinary oxalate: P = 0.00) in stone formers in comparison to the age-adjusted control. These findings observed in the current study were consistent with previous animal and human studies.

In the current study, stone analysis was done in all cases, and calcium oxalate stones were found in 40 patients (83.3%); 6 patients (12.5%) had phosphate and 2 patients (4.16%) had mix components. As stone formers have higher levels of testosterone (both free and total) and high levels of urinary oxalate in comparison to the control group, the finding of the maximum number of calcium oxalate stone in cases may help to establish the relation between serum testosterone and urinary oxalate. As stone analysis was not performed in previous reported studies, the current study may provide positive contributions to establish the relationship of serum testosterone to calcium oxalate stones.

Men with high testosterone levels may not develop stones due to some protective mechanism against high testosterone levels. More research is an integral requirement in the future to find out the probable protective mechanism. Due to a limited case number, we cannot strongly point out that relation. A long-term study and a large cohort may give us stronger evidence in the near future.

CONCLUSION

There is a paucity of research to establish the relationship between sex hormones and urolithogenesis in humans. In this current prospective study we have observed a statistically significant, higher level of free and total testosterone and 24 hours of urinary oxalate in stone formers compared to control. Serum testosterone has a weak positive correlation to urinary oxalate in stone formers and a higher number of patients had calcium oxalate stones. So far, the association between serum gonadal steroids and urolithiasis in males received only limited attention, and the recommendation for steroid investigation as a basic evaluation to rule out treatable systemic causes in urolithiasis patients is warranted. Considering consistent data on sex hormones and urolithiasis, further evaluation in a large cohort is needed to establish the relationship reliably in the future.

FIGURES

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