Age of study population and year of publication modified the relationship between testosterone and CVD .
Results were largely confirmed by separate analyses of free- and bioavailable testosterone .
The systematic review displayed no association between endogenous testosterone and risk for CVD in middle-aged men .
In elderly men , testosterone may weakly protect against CVD .
Alternatively , low testosterone may indicate a poor general health
CONTEXT The literature provides no clear answer as to whether low endogenous testosterone increases risk of cardiovascular disease ( CVD ) in healthy men .
OBJECTIVE Our purpose was to estimate the predictive value of testosterone for CVD and to identify study features explaining conflicting results .
Endogenous Sex Hormones and Cardiovascular Disease Incidence in Men
Context Studies of the role of endogenous sex hormones in  cardiovascular disease ( CVD ) in men have been inconclusive . Contribution A total of 2084 men from 2 Framingham Heart Study cohorts had levels of  total serum estrogen , testosterone , and dehydroepi and rosterone sulfate ( DHEA-S )  measured in 1981 to 1985 for the original cohort and in 1987 to 1991 for the offspring cohort . Testosterone and DHEA-S levels were not associated with CVD risk . Estrogen levels were inversely related : Risk for CVD in the highest quartile was 0.68 ( 95 % CI , 0.50 to 0.92 ) times that in the lowest level . Caution s Investigators studied only white men and did not study free unbound hormone levels . Implication s Endogenous estrogen may be vasculoprotective in men , which is in contrast to the effects of exogenous estrogen . The Editors Male sex is an independent risk factor for cardiovascular disease ( CVD ) ( 1 ) . Scientists have postulated that the 5- to 10-year lag period in CVD incidence in women ( compared with men ) may be related to differences in endogenous sex hormones ( 27 ) . Indeed , substantial evidence suggests that sex hormones ( testosterone , estrogen , and dehydroepi and rosterone sulfate [ DHEA-S ] ) influence traditional and newer CVD risk factors ( 27 ) . Interest in the role of sex hormones in the pathogenesis of CVD has been rekindled by the observation that men with genetic defects of estrogen synthesis ( 8) or action ( 9 ) develop premature atherosclerosis . In addition , genetic variation in estrogen receptor- has been associated with prevalent CVD ( 10 , 11 ) , and and rogen and estrogen receptor expression in coronary arteries has been reported to influence coronary atherosclerosis in men ( 12 ) . In contrast to the aforementioned data , prospect i ve studies relating circulating sex hormone levels to incident CVD in men have been inconclusive . For example , low serum testosterone levels have been associated with greater progression of sub clinical atherosclerosis in 2 previous investigations ( 13 , 14 ) , but other studies have reported no association of testosterone levels with CVD events ( 1521 ) . On a parallel note , low DHEA-S levels have been linked to greater CVD risk in some studies ( 18 , 2224 ) but not in other studies ( 13 , 20 , 2529 ) . Investigations relating serum estradiol levels to CVD risk in men have generally found no statistically significant association ( 1520 ) . Some previous investigations were limited by modest sample sizes ( 14 , 17 , 18 , 22 , 25 , 26 ) ; an insufficient number of CVD events ( 1518 , 22 , 23 , 26 ) ; and , in some instances , a retrospective study design ( 1721 , 25 , 26 ) . In addition , some reports ( 15 , 22 , 24 ) focused on CVD death ( they did not evaluate nonfatal CVD events ) . Thus , a large prospect i ve community-based study relating sex hormones to CVD risk with adequate power to detect modest potential associations is needed . Accordingly , we evaluated the associations of serum levels of sex hormones that were measured at a routine baseline examination with CVD incidence in a prospect ively assembled cohort of participants . Methods Study Sample The Framingham Heart Study , a prospect i ve study of the risk factors for the development of heart disease and stroke , began in 1948 with the recruitment of 5209 men and women between 30 and 60 years of age who resided in Framingham , Massachusetts ( 30 ) . The Framingham Offspring Study began in 1971 with the recruitment of 5124 participants who were the children of the original cohort and the spouses of the children ( 31 ) . Participants in the original cohort are examined every 2 years , while offspring cohort members are assessed every 4 years . At each Framingham Heart Study examination , attendees undergo a physical examination and laboratory assessment of risk factors ( 31 ) . We evaluated 2789 men who attended the 17th biennial examination ( 19811983 ) of the original cohort or the fourth quadrennial examination ( 19871991 ) of the offspring cohort . We measured serum total testosterone and estradiol levels at these examinations , and we measured DHEA-S levels at the 18th examination ( 19831985 ) for the original cohort and at the fourth examination for the offspring cohort . We excluded 705 men because of prevalent CVD ( n= 541 ) and nonavailable testosterone data ( n= 164 ) . After exclusions , 2084 men ( 74.7 % ; 525 original cohort participants ) without previous CVD were eligible . Data on serum estradiol levels and serum DHEA-S levels were available in 2047 men and 1928 participants , respectively . All participants gave written informed consent , and the institutional review board at the Boston Medical Center approved the study protocol . Biochemical Assessment of Sex Hormones As described previously ( 32 ) , we measured total testosterone , total estradiol , and DHEA-S levels from serum sample s by using radioimmunoassays ( Diagnostic Products Corp. , Los Angeles , California ) for total testosterone ( interassay coefficient of variation , 11 % ) , total estradiol ( interassay coefficient of variation , 4 % ) , and DHEA-S ( interassay coefficient of variation , 11 % ) . We also measured serum luteinizing hormone levels at the baseline examinations ( interassay coefficient of variation , 6 % ) . Cardiovascular Outcomes All participants were under continuous surveillance for the occurrence of  CVD events and death . Participants are evaluated periodically at the Framingham Heart Study and through health history up date s between examinations ( obtained via telephone interviews ) . Three experienced investigators obtained and review ed hospitalization and physician office visit records . We defined incident CVD as coronary heart disease ( recognized or unrecognized myocardial infa rct ion , angina pectoris , coronary insufficiency , or coronary heart disease death ) , cerebrovascular disease ( stroke or transient ischemic attack ) , congestive heart failure ( by Framingham criteria ) , or peripheral vascular disease ( intermittent claudication ) . Criteria for the diagnoses of cardiovascular events have been described elsewhere ( 33 ) . We considered that an unrecognized myocardial infa rct ion occurred if we found electrocardiographic evidence of clinical ly significant loss of R waves or appearance of pathologic Q waves on serial tracings in the absence of a clinical ly recognized event ( 33 ) . We defined the follow-up period a priori as 10 years from the baseline examination ( up to 1995 for the original cohort and 2002 for the offspring cohort ) to permit equal duration s of follow-up of original and offspring cohort participants and because sex hormone levels change considerably with age ( 34 ) . The analyses that combined the original and offspring cohorts had greater statistical power and allowed us to evaluate participants over a wider age range . Statistical Analyses Serum testosterone levels were normally distributed . Serum estradiol and DHEA-S levels were skewed and were log-transformed . We examined the associations between baseline sex hormone levels and CVD incidence during follow-up ( separate analyses for each hormone ) . We chose incident CVD as the outcome because the effects of sex hormones are not limited to a given vascular territory and this maximized our statistical power and limited multiple statistical testing ( as opposed to analysis for each CVD component ) . We stratified all analyses by the cohort ( offspring cohort vs. original cohort ) . We verified that the assumption of proportionality of hazards was satisfied for each hormone . We calculated age- and multivariable-adjusted 10-year incidence rates for CVD for each hormone quartile ( 35 ) . We prespecified 2 types of models : Primary analyses evaluated the sex hormones as continuous variables to maximize statistical power ( model A ) , and additional analyses compared CVD risk in hormone quartiles 2 to 4 with that in quartile 1 ( referent ) ( model B ) . These models facilitated assessment of potential nonlinear relations . For each hormone , we used proportional hazards regression ( 36 ) that adjusted for 1 ) age alone and 2 ) age , smoking , systolic and diastolic blood pressure , antihypertensive medication use , ratio of total and high-density lipoprotein ( HDL ) cholesterol , diabetes mellitus , and body mass index ( BMI ) . We evaluated models adjusted for age alone because some risk factors may fall along the causal pathway from estradiol to CVD . Adjustment for BMI was performed because adiposity is a strong correlate of sex hormone levels ( 37 ) and of sex hormonebinding globulin ( 38 ) . Sex hormonebinding globulin strongly influences measurements of total circulating sex hormone levels and the amount of bound hormone versus free hormone . We also evaluated models without BMI as a covariate to assess whether adjustment for BMI attenuated relations of sex hormones with CVD and models that were adjusted additionally for the use of aspirin or lipid-lowering medications , alcohol consumption , and education level . We incorporated statistical interaction terms to evaluate effect modification by age , BMI , smoking status , systolic blood pressure , and total cholesterolHDL cholesterol ratio . To gain additional insights into potential nonlinearity of associations between hormone levels and CVD risk , we examined generalized additive Cox models using penalized splines ( 39 , 40 ) for hormones that were statistically significantly related to CVD risk . Because potential relationships of sex hormones to CVD risk may be mediated by the development of risk factors during follow-up , we prespecified examination of time-dependent Cox models ( updating established CVD risk factors [ covariates in the multivariable-adjusted proportional hazards regression ] every 4 years at follow-up examinations ) for analyses of any sex hormone that was statistically significantly related to CVD events in the initial analyses . Additional Analyses We performed secondary analyses relating CVD risk to the estradioltestosterone ratio ( 37 , 41 ) . In addition , we investigated whether hypogonadism was related to CVD risk . We defined hypogonadism empirically as a serum testosterone level less than 10.4 nmol/L (
Age of study population and year of publication modified the relationship between testosterone and CVD .
Results were largely confirmed by separate analyses of free- and bioavailable testosterone .
The systematic review displayed no association between endogenous testosterone and risk for CVD in middle-aged men .
In elderly men , testosterone may weakly protect against CVD .
Alternatively , low testosterone may indicate a poor general health
CONTEXT The literature provides no clear answer as to whether low endogenous testosterone increases risk of cardiovascular disease ( CVD ) in healthy men .
OBJECTIVE Our purpose was to estimate the predictive value of testosterone for CVD and to identify study features explaining conflicting results .