men , aged > 30 years , with type 2 diabetes were recruited from barnsley hospital nhs trust , barnsley , u.k . most of the subjects were recruited from the retinal screening program , which is attended by virtually all patients with diabetes in the barnsley area . subjects were given written and verbal information regarding the study , and 355 men gave their informed consent to take part . the study population comprised patients with diabetes usually managed in primary care facilities as well as secondary care patients . other measurements included blood pressure , a1c , nonfasting lipid levels , height , weight , and waist circumference . the main data from the study were published previously in diabetes care ( 2 ) . patients were seen in the morning between 8:00 and 10:00 a.m. symptoms of hypogonadism were assessed by completion of the androgen deficiency in the aging male ( adam ) questionnaire , which was validated to assess hypogonadism in aging men ( 19 ) . serum total testosterone , total estradiol , and shbg were measured by an enzyme - linked immunosorbent assay using commercially available kits ( drg diagnostics , marburg , germany ) . bioavailable testosterone was determined by a modification of the ammonium sulfate precipitation method described by tremblay and dube ( 20 ) . free testosterone was calculated from total testosterone and shbg by the formula of vermeulen et al . . these methods of assessing bioavailable and free testosterone have been used in previous studies from our research team and have determined to be reliable for the assessment of men with diabetes and vascular disease ( 17 ) . a1c was assessed using a menarini analyser ha8160 ( menarini diagnostics , florence , italy ) . serum lipid parameters were assessed by olympus analyzers ( olympus diagnostics , hamburg , germany ) . testosterone and shbg were log - normally distributed and were converted to a normal distribution to allow use of student 's t test for comparison of group means . with smaller groups , the normal distribution was assessed using single - sample kolmogorov - smirnov testing . the two - sample kolmogorov - smirnov test was used to compare groups when data did not fulfill the normal distribution . results were initially considered statistically significant at p < 0.05 . because of multiple statistical testing patients were seen in the morning between 8:00 and 10:00 a.m. symptoms of hypogonadism were assessed by completion of the androgen deficiency in the aging male ( adam ) questionnaire , which was validated to assess hypogonadism in aging men ( 19 ) . serum total testosterone , total estradiol , and shbg were measured by an enzyme - linked immunosorbent assay using commercially available kits ( drg diagnostics , marburg , germany ) . bioavailable testosterone was determined by a modification of the ammonium sulfate precipitation method described by tremblay and dube ( 20 ) . free testosterone was calculated from total testosterone and shbg by the formula of vermeulen et al . . these methods of assessing bioavailable and free testosterone have been used in previous studies from our research team and have determined to be reliable for the assessment of men with diabetes and vascular disease ( 17 ) . a1c was assessed using a menarini analyser ha8160 ( menarini diagnostics , florence , italy ) . serum lipid parameters were assessed by olympus analyzers ( olympus diagnostics , hamburg , germany ) . testosterone and shbg were log - normally distributed and were converted to a normal distribution to allow use of student 's t test for comparison of group means . with smaller groups , the normal distribution was assessed using single - sample kolmogorov - smirnov testing . the two - sample kolmogorov - smirnov test was used to compare groups when data did not fulfill the normal distribution . results were initially considered statistically significant at p < 0.05 . because of multiple statistical testing , we performed a bonferroni correction to minimize the chance of type 2 errors . in our cross - section of 355 men with type 2 diabetes , 186 were not treated with statins . of 169 men treated with statins , 81 were treated with atorvastatin , 66 with simvastatin , 15 with pravastatin , and 7 with other statins ( 3 with fluvastatin , 1 with cerivastatin , and 3 with  unknown statin  ) . patients treated with statins did not significantly differ from untreated individuals in age , waist circumference , bmi , a1c , or blood pressure ( table 1 ) . total cholesterol and ldl cholesterol levels were lower in men taking statins , but there were no significant differences in hdl cholesterol or triglyceride levels ( data not shown ) . mean sex hormone levels , measures of obesity , and cholesterol levels in men treated with any statin , atorvastatin , and simvastatin compared with untreated men p values given for student 's t test comparing treated patients with the untreated group . total testosterone was significantly lower in the statin and atorvastatin groups but not in the simvastatin group . bioavailable and free testosterone levels were not significantly lower in any group . both statins were associated with lower cholesterol levels , but none of the groups were significantly different in terms of obesity . total testosterone levels were significantly lower in men treated with statins , and there was a trend toward lower shbg levels , but this did not reach statistical significance ( table 1 ) . bioavailable testosterone , calculated free testosterone , and serum estrogen levels were not significantly different between the groups . the symptom score from the adam questionnaire was not significantly altered in those men receiving statin therapy . there were sufficient numbers of men treated with simvastatin and atorvastatin to consider these groups more closely ( tables 1 and 2 ) . these groups were not significantly different from untreated men in terms of bmi , waist circumference , blood pressure , a1c , or age . total cholesterol and ldl cholesterol levels were lower in both groups compared with those in untreated men but were not significantly different between simvastatin- and atorvastatin - treated groups . men treated with simvastatin did not have significantly different total , bioavailable , or free testosterone , estradiol , or shbg levels than untreated men ( fig . 1 and table 1 ) . in contrast , men treated with atorvastatin had an average total testosterone level 1.96 nmol / l ( 56 ng / dl ) less than that in untreated men . there was a trend toward lower shbg levels in this group ( 35.3 vs. 27.6 nmol / l , p = 0.022 ) . further analysis revealed an apparent dose - response relationship , with the lowest testosterone levels seen in men taking higher doses of atorvastatin ( table 3 ) . nmol / l ( 108 ng / dl ) less than that of untreated men ( table 3 ) , but this value did not reach statistical significance ( p = 0.017 ) . shbg was also reduced without reaching significance ( p = 0.043 ) , but free and bioavailable testosterone levels were unaltered . no significant differences were seen in sex hormone levels when the simvastatin - treated men were split into similar groups ( data not shown ) . there were no significant differences in age , bmi , waist circumference , blood pressure , or a1c in any of the atorvastatin- or simvastatin - treated subgroups . characteristics of patients untreated with statins and those treated with atorvastatin and simvastatin p values given for student 's t test . there were no significant differences in age , anthropomorphic data , glycemic control , or blood pressure . total and ldl cholesterol are lower in the statin - treated group , reflecting the primary action of the drugs . mean testosterone levels in untreated men and those treated with atorvastatin or simvastatin ; 95% cis are shown . international guidelines suggest that testosterone replacement is invariably warranted when the total testosterone level is < 8 nmol / l ( 231 ng / dl ) or the free testosterone level is < 0.18 nmol / l ( 346 ng / dl ) or a free testosterone between 0.18 and 0.25 nmol / l . * p < 0.01 ; + p < 0.05 . average testosterone , shbg , and measures of obesity in men treated with atorvastatin split into two groups : those treated with 10 mg and those treated with 20 mg or more the 10-mg atorvastatin group was compared with the no statin group with student 's t test ; significant results are shown in boldface . the 20-mg atorvastatin group was compared with the no statin group using a two - sample kolmogorov - smirnov test . there is a trend toward lower total testosterone and shbg levels in men taking the higher doses of atorvastatin , but this does not reach statistical significance . in our cross - section of 355 men with type 2 diabetes , 186 were not treated with statins . of 169 men treated with statins , 81 were treated with atorvastatin , 66 with simvastatin , 15 with pravastatin , and 7 with other statins ( 3 with fluvastatin , 1 with cerivastatin , and 3 with  unknown statin  ) . patients treated with statins did not significantly differ from untreated individuals in age , waist circumference , bmi , a1c , or blood pressure ( table 1 ) . total cholesterol and ldl cholesterol levels were lower in men taking statins , but there were no significant differences in hdl cholesterol or triglyceride levels ( data not shown ) . mean sex hormone levels , measures of obesity , and cholesterol levels in men treated with any statin , atorvastatin , and simvastatin compared with untreated men p values given for student 's t test comparing treated patients with the untreated group . total testosterone was significantly lower in the statin and atorvastatin groups but not in the simvastatin group . bioavailable and free testosterone levels were not significantly lower in any group . both statins were associated with lower cholesterol levels , but none of the groups were significantly different in terms of obesity . total testosterone levels were significantly lower in men treated with statins , and there was a trend toward lower shbg levels , but this did not reach statistical significance ( table 1 ) . bioavailable testosterone , calculated free testosterone , and serum estrogen levels were not significantly different between the groups . the symptom score from the adam questionnaire was not significantly altered in those men receiving statin therapy . there were sufficient numbers of men treated with simvastatin and atorvastatin to consider these groups more closely ( tables 1 and 2 ) . these groups were not significantly different from untreated men in terms of bmi , waist circumference , blood pressure , a1c , or age . total cholesterol and ldl cholesterol levels were lower in both groups compared with those in untreated men but were not significantly different between simvastatin- and atorvastatin - treated groups . men treated with simvastatin did not have significantly different total , bioavailable , or free testosterone , estradiol , or shbg levels than untreated men ( fig . 1 and table 1 ) . in contrast , men treated with atorvastatin had an average total testosterone level 1.96 nmol / l ( 56 ng / dl ) less than that in untreated men . there was a trend toward lower shbg levels in this group ( 35.3 vs. 27.6 nmol / l , p = 0.022 ) . further analysis revealed an apparent dose - response relationship , with the lowest testosterone levels seen in men taking higher doses of atorvastatin ( table 3 ) . nmol / l ( 108 ng / dl ) less than that of untreated men ( table 3 ) , but this value did not reach statistical significance ( p = 0.017 ) . shbg was also reduced without reaching significance ( p = 0.043 ) , but free and bioavailable testosterone levels were unaltered . no significant differences were seen in sex hormone levels when the simvastatin - treated men were split into similar groups ( data not shown ) . there were no significant differences in age , bmi , waist circumference , blood pressure , or a1c in any of the atorvastatin- or simvastatin - treated subgroups . characteristics of patients untreated with statins and those treated with atorvastatin and simvastatin p values given for student 's t test . there were no significant differences in age , anthropomorphic data , glycemic control , or blood pressure . total and ldl cholesterol are lower in the statin - treated group , reflecting the primary action of the drugs . mean testosterone levels in untreated men and those treated with atorvastatin or simvastatin ; 95% cis are shown . international guidelines suggest that testosterone replacement is invariably warranted when the total testosterone level is < 8 nmol / l ( 231 ng / dl ) or the free testosterone level is < 0.18 nmol / l ( 346 ng / dl ) or a free testosterone between 0.18 and 0.25 nmol / l . * p < 0.01 ; + p < 0.05 . average testosterone , shbg , and measures of obesity in men treated with atorvastatin split into two groups : those treated with 10 mg and those treated with 20 mg or more the 10-mg atorvastatin group was compared with the no statin group with student 's t test ; significant results are shown in boldface . the 20-mg atorvastatin group was compared with the no statin group using a two - sample kolmogorov - smirnov test . there is a trend toward lower total testosterone and shbg levels in men taking the higher doses of atorvastatin , but this does not reach statistical significance . this is the first study to analyze fully testosterone levels and hypogonadal symptoms in comparison with statin use in a population receiving routine medical management . those treated with atorvastatin had lower levels of total testosterone with a trend toward lower shbg compared with untreated men , whereas those treated with simvastatin were not significantly affected . statin treatment did not significantly affect the biologically active fractions of testosterone , symptoms of hypogonadism , or estradiol levels . this study demonstrates that treatment with statins in this group can be a confounding factor in the assessment of hypogonadism . total testosterone is the primary test used in the diagnosis of hypogonadism , and the effect of atorvastatin could potentially lead to misdiagnosis of the condition in men with normal free and bioavailable testosterone levels . alternatively , it is possible that reductions in total testosterone without changes in bioactive testosterone fractions have clinical effects in view of findings suggesting that shbg - bound testosterone may be biologically active ( 13 ) . the adam questionnaire failed to detect an increase in hypogonadal symptoms in groups with lower total testosterone levels , but the questionnaire does not correlate closely with testosterone levels , and men with diabetes have a high level of false - positive hypogonadal symptoms ( 2 ) such as erectile dysfunction owing to vascular and neuropathic factors , medications , and depression . atorvastatin is a more potent statin than simvastatin , thus causing a greater reduction in the total cholesterol and hence total testosterone levels . no patients in our study were treated with other potent statins such as rosuvastatin so we are unable to confirm that atorvastatin reduces testosterone and shbg levels secondary to more potent effects on cholesterol levels . indeed , cholesterol and other lipid fraction levels were not significantly different between simvastatin- and atorvastatin - treated groups . in a normal physiological state , luteinizing hormone ( lh ) promotes uptake of cholesterol by the testis and stimulates testosterone synthesis . a reduction in testosterone is sensed by the hypothalamic - pituitary axis and leads to greater lh release , which completes a negative feedback loop and maintains testosterone levels . the apparent failure of the hypothalamic - pituitary - testicular axis to respond and maintain testosterone levels in the statin - treated patients in our study may be explained by the hypogonadal - obesity - adipocytokine hypothesis ( 1 ) . the majority of the patients in our study were overweight or obese . in this population , greater production of adipocytokines such as tumor necrosis factor- , interleukin-6 , and leptin and increased estradiol from metabolism of testosterone by aromatase in adipose tissue inhibit lh release from the pituitary gland , which leads to lower circulating testosterone levels . in our study , gonadotrophin levels were only tested in men with total testosterone levels < 12 mmol / l ( 2 ) , leaving us unable to test this hypothesis . the most likely reason that bioavailable and free testosterone levels are unaltered despite lower total testosterone is a homeostatic mechanism via reduced shbg production . an alternative hypothesis is that atorvastatin causes a primary reduction in shbg with consequent reductions in total testosterone . there was a consistent trend toward low shbg levels in all groups with reduced levels of total testosterone , although these low levels did not reach statistical significance . shbg is produced in the liver , the primary site of action of the statins , but the mechanism by which statins could alter shbg is unknown . shbg levels are known to be modulated by a number of factors including downregulation by insulin resistance and upregulation by estrogens ( 21 ) . we are aware of one clinical trial assessing the effects of atorvastatin on testosterone levels in men . the results showed a nonsignificant fall in total testosterone and no change in shbg ( 4 ) . these data are insufficient to confirm or refute our findings relating to atorvastatin , and it may be that the study allowed insufficient time for changes to develop . some trials have shown that simvastatin reduces serum testosterone levels ( 911 ) , whereas others have shown no effect ( 68 ) . our data suggest that any effect of simvastatin in reducing serum testosterone levels is not clinically significant in men with type 2 diabetes . we are not aware of any previous evidence for an effect of any statin on shbg levels . nmol / l ( 231 ng / dl ) are hypogonadal , that men with total testosterone levels > 12 nmol / l ( 346 ng / dl ) do not have hypogonadism , and that men with levels between 8 and 12 nmol / l need consideration for treatment depending on their clinical picture ( 18 ) . an endocrine society clinical practice guideline suggested a diagnostic cutoff value of testosterone of < 10.4 our findings are important in this context because statin treatment was associated with lower total testosterone levels of 11.9 nmol / l ( 340 ng / dl ) ( versus 13.4 nmol / l [ 384 ng / dl ] ) . men treated with 20 mg / day atorvastatin had an average total testosterone level of only 9.6 nmol / l ( 275 ng / dl ) , which is 3.8 nmol / l ( 109 ng / dl ) lower than that of men not treated with statins . thus , statin treatment may lead to reductions in total testosterone levels to < 12 or 10.4 nmol / l in many men but will not significantly alter bioavailable or free testosterone levels or hypogonadal symptoms . we recommend a low threshold for measuring or calculating bioavailable or free testosterone in men receiving statin therapy . it has now been confirmed that reductions in total testosterone are accompanied by similar changes in free and bioavailable testosterone and a high prevalence of hypogonadal symptoms ( 2 ) . furthermore , short - term studies in small numbers of hypogonadal diabetic men have shown improvements in glycemic control , central obesity , and serum leptin during testosterone replacement therapy ( 23,24 ) . other short - term studies have shown beneficial effects on further cardiovascular risk factors including total cholesterol levels ( 25 ) . in this context , the assessment of hypogonadism in men with type 2 diabetes is likely to increase in frequency . assessment of the clinical syndrome of hypogonadism can be challenging in this group because of the confounding effects of vascular disease , psychological factors , and medications on symptoms such as erectile dysfunction . this assessment is complicated by low shbg levels , which have long been associated with insulin resistance , leading to suggestions that low testosterone levels in type 2 diabetes are due to low shbg rather than to reductions in bioactive testosterone fractions . this suggestion has been refuted by studies showing low free and bioavailable testosterone levels in men with type 2 diabetes ( 2 ) and meta - analysis data suggesting relatively small changes in shbg in men with diabetes ( 22 ) . the realization that statin treatment may reduce total testosterone and shbg levels in this patient group serves to refocus attention to a subgroup who are particularly likely to have low shbg levels with the potential for a misdiagnosis of hypogonadism . in summary , this large data set is the first to suggest a significant effect of statins in lowering total testosterone and shbg levels in a population of men with type 2 diabetes . the findings have important implications for the diagnosis of hypogonadism in men receiving statin treatment . the opportunity to conduct similar studies of men with type 2 diabetes , comparing men treated with statins to untreated men , has now probably passed owing to the almost ubiquitous use of statins in this group . limitations of this study are its observational nature and the resultant inability to prove causality . statin - treated men did not differ from other men in terms of age , blood pressure , obesity , or glycemic control , but unidentified confounders can not be excluded . therefore further longitudinal or interventional studies are also needed to assess the effects of statins on androgen status in various patient groups and could include assessment of gonadotrophins and prolactin , which were not measured here . researchers should also investigate mechanisms that lead to changes in shbg and total testosterone in this context .
objectivethere is a high prevalence of hypogonadism in men with type 2 diabetes . 
 this will lead to an increase in assessments of hypogonadism . 
 statins could potentially decrease testosterone levels by reducing the availability of cholesterol for androgen synthesis . 
 we compared testosterone levels and hypogonadal symptoms with statin use in a cross - sectional study of 355 men with type 2 diabetes.research design and methodstotal testosterone , sex hormone  binding globulin ( shbg ) , and estradiol were measured by an enzyme - linked immunosorbent assay . 
 bioavailable testosterone was measured by the modified ammonium sulfate precipitation method . 
 free testosterone was calculated using vermeulen 's formula . 
 symptoms of hypogonadism were assessed using the androgen deficiency in the aging male questionnaire.resultsstatins were associated with lower total testosterone ( 11.9 vs. 13.4 nmol / l , p = 0.006 ) and a trend toward lower shbg ( 29.4 vs. 35.3 nmol / l , p = 0.034 ) compared with no treatment . 
 bioavailable testosterone , free testosterone , estradiol , and hypogonadal symptoms were not affected . 
 subanalysis showed that atorvastatin was associated with reduced total testosterone ( 11.4 vs. 13.4 nmol / l , p = 0.006 ) and a trend toward reduced shbg ( 27.6 vs. 35.3 nmol / l , p = 0.022 ) compared with no treatment , and there was an apparent dose - response effect with the lowest levels of total testosterone seen in men treated with 20 mg atorvastatin ( 9.6 nmol / l , p = 0.017 ) . 
 simvastatin use was not associated with significant reductions in testosterone or shbg levels.conclusionsassessing androgen status using total testosterone in men with type 2 diabetes treated with statins , particularly atorvastatin , may potentially lead to diagnostic error . 
 levels of bioavailable testosterone or free testosterone are recommended for the assessment of hypogonadism in this group if total testosterone levels are borderline .