J C E M
O N L I N E
Association between sex hormones and adiposity: Qualitative differences in women and men in the Multi-Ethnic Study of Atherosclerosis Morgana L. Mongraw-Chaffin1,2, Cheryl A. M. Anderson1,2, Matthew A. Allison1, Pamela Ouyang3, Moyses Szklo2, Dhananjay Vaidya3, Mark Woodward2,4,5, Sherita Hill Golden2,3 1. Department of Family and Preventive Medicine, School of Medicine, University of California San Diego, San Diego CA; 2. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD; 3. Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD; 4. The George Institute for Global Health, The University of Sydney, Sydney, Australia; 5. The George Institute for Global Health, Nuffield Department of Population Health, University of Oxford, Oxford, UK
Context: Sex hormones may influence adipose tissue deposition, possibly contributing to sex disparities in cardiovascular disease (CVD) risk. Objective: We hypothesized that associations of sex hormone levels with visceral and subcutaneous fat differ by sex. Design, Setting, and Participants: Participants were from the Multi-Ethnic Study of Atherosclerosis with sex hormone levels at baseline and visceral and subcutaneous fat measurements from computed tomography at visit 2 or 3 (n⫽1835). Main Outcome Measures: Multivariable linear regression was used to investigate the relationships between sex hormones and adiposity. Testing for interaction by sex, race/ethnicity, and age was conducted. Results: In adjusted models, there was a modest significant positive association between estradiol and visceral fat in both sexes (% difference in visceral fat for 1% difference in estradiol in women: 5.44 [1.82, 9.09] in men: 8.22 [0.61, 16.18]). Higher bioavailable testosterone was significantly associated with higher visceral and subcutaneous fat in women and the reverse in men (women: 14.38 [10.23, 18.69] men: -7.69 [-13.06, -1.00]). Higher dehydroepiandosterone was associated with higher visceral fat in women (women: 7.57 [1.71, 13.88]), but not in men (-2.47 [-8.88, 4.29]). Higher sex hormone binding globulin was associated with significantly lower levels of adiposity in both sexes (women: -24.42 [-28.11, -20.55] men: -27.39 [-32.97, -21.34]). There was no significant interaction by race/ethnicity or age. Conclusion: Sex hormones are significantly associated with adiposity, and the associations of androgens differ qualitatively by sex. This heterogeneity may help explain the complexity of the contribution of sex hormones to sex differences in CVD.
S
exual dimorphism in body composition has been a topic of interest for more than 50 years (1), and has been suggested to explain some of the sex differences in cardiovascular disease and mortality (2). Despite this in-
terest, it remains unclear why women have more subcutaneous fat, but less visceral fat than men (2). One suggestion is that sex hormones play a large role in determining healthy body composition (3). Estrogen has
ISSN Print 0021-972X ISSN Online 1945-7197 Printed in U.S.A. Copyright © 2015 by the Endocrine Society Received July 14, 2014. Accepted January 22, 2015.
Abbreviations:
doi: 10.1210/jc.2014-2934
J Clin Endocrinol Metab
jcem.endojournals.org
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1
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Sex hormones and adiposity
been proposed to explain the healthier fat distributions of women, (3) and it has been suggested that in men testosterone has a significant role in determining fat distribution and maintaining lean mass (4, 5). There are few data about the effect of estradiol on visceral adiposity in men, (6) or of free testosterone on adiposity in women (7). One possible reason for this complexity is that the relationships between sex hormones and body composition are different, and potentially even reversed, for women and men. Although there is increasing evidence that fat distribution may differ by race, (8) there is sparse evidence about sex hormone differences by race. Using the context provided above, the aim of this study was to determine if sex hormones are cross-sectionally associated with computed tomography (CT)-derived (CT) measures of visceral and subcutaneous fat by sex and race/ethnicity in the MultiEthnic Study of Atherosclerosis (MESA). Research Design and Methods: Study Population MESA is a longitudinal multisite study with baseline data collection on 6814 participants aged 45 to 84 years in 2000 to 2002, and free of known cardiovascular disease (9). MESA’s Abdominal Body Composition, Inflammation and Cardiovascular Disease Ancillary Study (n ⫽ 1947) consists of a 30% random sample of the MESA cohort that received CT scans divided between visits 2 and 3 (2002–2005). Excluding 24 participants with uncodeable scans and 88 women with unknown menopausal status at visit 1, gave a final sample size of 1835. For this analysis, we combined sex hormone data and covariates collected at baseline and body composition data from scans conducted at visits 2 and 3. Institutional Review Board (IRB) approval for the MESA study was provided by multiple institutional IRBs and all participants provided informed consent. Measurement of Body composition and Sex Hormones CT scans of the abdomen were used to measure visceral and subcutaneous fat mass by semiautomated segmentation of the body compartments using the Medical Image Processing, Analysis, and Visualization (MIPAV) software program from the National Institutes of Health (NIH). Total visceral and subcutaneous fat areas (separately) were defined as the average of two CT slices obtained at the L4/L5 vertebrae. Additional information on the measurement of visceral and subcutaneous fat is available in Supplemental Text 1. Sex hormone levels were measured at baseline for all male and all postmenopausal female participants with morning fasting serum samples, as previously described (10).
J Clin Endocrinol Metab
Statistical Analysis We calculated means and standard deviations or medians and interquartile ranges for baseline characteristics by sex. We calculated the means and 95% confidence intervals of visceral fat and subcutaneous fat respectively for sex-specific quintiles of each sex hormone for women and men separately. We then used the Cuzick nonparametric test for trend across ordered groups to assess the significance of trends in body composition by increasing sex hormone quintile. We used multivariable linear regression to determine if higher sex hormone levels at baseline were associated with CT measures of adiposity at visits 2 and 3. Based on the understanding that the hormone distributions might not overlap for women and men, we decided a priori to create separate models for women and men. All body composition and sex hormone values were natural log transformed and results are reported as back transformed percent differences. We formally tested for interaction by race/ethnicity using interaction terms in the model. We included models with different levels of adjustment for confounding, including adjustment for other sex hormones. We then created more parsimonious final models by retaining only those variables that were significant at the P ⬍ .05 level in the full models for either men or women, in order to test for heterogeneity using the same model for both sexes. We also formally tested for interactions by sex using Wald tests. We performed sensitivity analyses to ensure that the estimates from the final regression model were robust to multiple conditions. Finally, we estimated the association between total testosterone and adiposity, in addition to the main models using bioavailable testosterone. Analyses were performed using Stata 11.
Results The final sample included 855 postmenopausal women and 936 men age 44 to 84 years at baseline. Women had significantly lower estradiol, bioavailable testosterone, DHEA, and visceral fat than men, but higher SHBG and subcutaneous fat (Supplemental Table 1). There were no differences in race/ethnicity. Figure 1 shows the unadjusted means and 95% confidence intervals of visceral fat and subcutaneous fat by sex-specific quintiles of estradiol, bioavailable testosterone, SHBG, and DHEA for women and men. Sex-specific hormone quintiles are given in Supplemental Table 2. For visceral fat (Figure 1A), there was a significant positive trend for estradiol, bioavailable testosterone, and DHEA, and a significant negative trend for SHBG in women. In men, higher quintiles of bioavailable testosterone, DHEA,
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 20 February 2015. at 22:03 For personal use only. No other uses without permission. . All rights reserved.
doi: 10.1210/jc.2014-2934
and SHBG were significantly associated with lower mean visceral fat. All trends between visceral fat and sex hormones were significant at the P ⬍ .05 level, except for the estradiol relationship in men. For subcutaneous fat (Figure 1B), results were similar to those for visceral fat, except that the relationship with estradiol in men was significantly positive and no significant trend was seen for DHEA in either women or men. Table 1 and Supplemental Table 3 show results from the adjusted models, which gave broadly similar, but attenuated results to those shown in Figure 1. We detected no interactions by race/ethnicity. In the final models, we found a significant interaction by sex for bioavailable testosterone and DHEA, but not for estradiol or SHBG for both visceral and subcutaneous fat models. Estimates remained similar when adjusting for other hormones. We observed few changes in the estimates with subgroup analysis, with estimates in the same direction as those from the main analysis (Supplemental Table 4). Finally, visceral fat estimates for total testosterone were similar to those for bioavailable testosterone, even after adjusting for SHBG (data not shown).
Discussion In the MESA study, significant qualitative differences by sex, but not race/ethnicity, exist in the relationship between selected sex hormones and CT-measured body composition. In men, androgens were negatively related in varying degrees to fat in the visceral and subcutaneous
jcem.endojournals.org
E3
compartments. This association was reversed for women. In contrast, SHBG was inversely associated with fat from both compartments for both women and men. In women, there was a significant, but modest, positive association between estradiol and visceral fat, while for men this association was also positive, but not significantly different. Studies in men have shown the importance of testosterone in maintaining healthy body composition (11). While the evidence for testosterone is strongest for its association with lean muscle mass, testosterone has been shown to play a role in the deposition of fat to different body compartments (5). Most of the previous studies are consistent with our findings. Studies in men generally found an inverse association between testosterone and adiposity, as well as an inverse association between SHBG and adiposity (4, 12–16). Studies in women found a positive association between testosterone and adiposity, (6, 7, 17–20) but an inverse association between SHBG and adiposity (17, 19 –21). Studies investigating the association between estradiol and adiposity have produced inconsistent findings; (4, 6, 7, 12, 20) however, the two studies that investigated these relationships using CT or MRI to measure body composition found results somewhat similar to ours (4, 7). Despite increasing interest in the role that sex hormones play in body composition, studies that simultaneously investigate the associations of both estrogen and androgen are rare (6, 7, 12, 20). Similarly, studies on sex hormones have predominantly focused on the health of either women or men, but not both, limiting inference about
Figure 1. A. Unadjusted mean visceral fat area by sex-specific sex hormone quintiles. B. Unadjusted mean subcutaneous fat area by sex-specific hormone quintiles.
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E4
Sex hormones and adiposity
J Clin Endocrinol Metab
Table 1. Percent difference in back-transformed visceral fat (ln cm2) for every percent difference in backtransformed sex hormone (ln nmol/liter) in 1835 participants aged 45– 84 in the MESA Body Composition ancillary study Visceral Fat
Women
Men
P-value for Heterogeneity by Sex
Unadjusted Model Estradiol Bioavailable Testosterone SHBG DHEA
Estradiol Bioavailable Testosterone SHBG DHEA Final Model
5.02 (1.01 9.42)
6.08 (-1.98, 15.03) ⴚ9.51 (-15.63, ⫺2.96)
17.25 (12.75, 22.14) -25.92 (-29.53, ⫺22.12) -23.66 (-28.82, ⫺17.3) 6.72 (0.60, 12.75) -10.42 (-16.47, ⫺4.69) Adjusted for: race/ethnicity ⫹ age ⫹ income ⫹ education 8.22 (4.39, 11.63) 17.35 (12.75, 22.14) -27.39 (-30.93, ⫺23.66) 10.52 (4.08, 17.35)
0.83
O N L I N E
Association between sex hormones and adiposity: Qualitative differences in women and men in the Multi-Ethnic Study of Atherosclerosis Morgana L. Mongraw-Chaffin1,2, Cheryl A. M. Anderson1,2, Matthew A. Allison1, Pamela Ouyang3, Moyses Szklo2, Dhananjay Vaidya3, Mark Woodward2,4,5, Sherita Hill Golden2,3 1. Department of Family and Preventive Medicine, School of Medicine, University of California San Diego, San Diego CA; 2. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD; 3. Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD; 4. The George Institute for Global Health, The University of Sydney, Sydney, Australia; 5. The George Institute for Global Health, Nuffield Department of Population Health, University of Oxford, Oxford, UK
Context: Sex hormones may influence adipose tissue deposition, possibly contributing to sex disparities in cardiovascular disease (CVD) risk. Objective: We hypothesized that associations of sex hormone levels with visceral and subcutaneous fat differ by sex. Design, Setting, and Participants: Participants were from the Multi-Ethnic Study of Atherosclerosis with sex hormone levels at baseline and visceral and subcutaneous fat measurements from computed tomography at visit 2 or 3 (n⫽1835). Main Outcome Measures: Multivariable linear regression was used to investigate the relationships between sex hormones and adiposity. Testing for interaction by sex, race/ethnicity, and age was conducted. Results: In adjusted models, there was a modest significant positive association between estradiol and visceral fat in both sexes (% difference in visceral fat for 1% difference in estradiol in women: 5.44 [1.82, 9.09] in men: 8.22 [0.61, 16.18]). Higher bioavailable testosterone was significantly associated with higher visceral and subcutaneous fat in women and the reverse in men (women: 14.38 [10.23, 18.69] men: -7.69 [-13.06, -1.00]). Higher dehydroepiandosterone was associated with higher visceral fat in women (women: 7.57 [1.71, 13.88]), but not in men (-2.47 [-8.88, 4.29]). Higher sex hormone binding globulin was associated with significantly lower levels of adiposity in both sexes (women: -24.42 [-28.11, -20.55] men: -27.39 [-32.97, -21.34]). There was no significant interaction by race/ethnicity or age. Conclusion: Sex hormones are significantly associated with adiposity, and the associations of androgens differ qualitatively by sex. This heterogeneity may help explain the complexity of the contribution of sex hormones to sex differences in CVD.
S
exual dimorphism in body composition has been a topic of interest for more than 50 years (1), and has been suggested to explain some of the sex differences in cardiovascular disease and mortality (2). Despite this in-
terest, it remains unclear why women have more subcutaneous fat, but less visceral fat than men (2). One suggestion is that sex hormones play a large role in determining healthy body composition (3). Estrogen has
ISSN Print 0021-972X ISSN Online 1945-7197 Printed in U.S.A. Copyright © 2015 by the Endocrine Society Received July 14, 2014. Accepted January 22, 2015.
Abbreviations:
doi: 10.1210/jc.2014-2934
J Clin Endocrinol Metab
jcem.endojournals.org
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 20 February 2015. at 22:03 For personal use only. No other uses without permission. . All rights reserved.
1
E2
Sex hormones and adiposity
been proposed to explain the healthier fat distributions of women, (3) and it has been suggested that in men testosterone has a significant role in determining fat distribution and maintaining lean mass (4, 5). There are few data about the effect of estradiol on visceral adiposity in men, (6) or of free testosterone on adiposity in women (7). One possible reason for this complexity is that the relationships between sex hormones and body composition are different, and potentially even reversed, for women and men. Although there is increasing evidence that fat distribution may differ by race, (8) there is sparse evidence about sex hormone differences by race. Using the context provided above, the aim of this study was to determine if sex hormones are cross-sectionally associated with computed tomography (CT)-derived (CT) measures of visceral and subcutaneous fat by sex and race/ethnicity in the MultiEthnic Study of Atherosclerosis (MESA). Research Design and Methods: Study Population MESA is a longitudinal multisite study with baseline data collection on 6814 participants aged 45 to 84 years in 2000 to 2002, and free of known cardiovascular disease (9). MESA’s Abdominal Body Composition, Inflammation and Cardiovascular Disease Ancillary Study (n ⫽ 1947) consists of a 30% random sample of the MESA cohort that received CT scans divided between visits 2 and 3 (2002–2005). Excluding 24 participants with uncodeable scans and 88 women with unknown menopausal status at visit 1, gave a final sample size of 1835. For this analysis, we combined sex hormone data and covariates collected at baseline and body composition data from scans conducted at visits 2 and 3. Institutional Review Board (IRB) approval for the MESA study was provided by multiple institutional IRBs and all participants provided informed consent. Measurement of Body composition and Sex Hormones CT scans of the abdomen were used to measure visceral and subcutaneous fat mass by semiautomated segmentation of the body compartments using the Medical Image Processing, Analysis, and Visualization (MIPAV) software program from the National Institutes of Health (NIH). Total visceral and subcutaneous fat areas (separately) were defined as the average of two CT slices obtained at the L4/L5 vertebrae. Additional information on the measurement of visceral and subcutaneous fat is available in Supplemental Text 1. Sex hormone levels were measured at baseline for all male and all postmenopausal female participants with morning fasting serum samples, as previously described (10).
J Clin Endocrinol Metab
Statistical Analysis We calculated means and standard deviations or medians and interquartile ranges for baseline characteristics by sex. We calculated the means and 95% confidence intervals of visceral fat and subcutaneous fat respectively for sex-specific quintiles of each sex hormone for women and men separately. We then used the Cuzick nonparametric test for trend across ordered groups to assess the significance of trends in body composition by increasing sex hormone quintile. We used multivariable linear regression to determine if higher sex hormone levels at baseline were associated with CT measures of adiposity at visits 2 and 3. Based on the understanding that the hormone distributions might not overlap for women and men, we decided a priori to create separate models for women and men. All body composition and sex hormone values were natural log transformed and results are reported as back transformed percent differences. We formally tested for interaction by race/ethnicity using interaction terms in the model. We included models with different levels of adjustment for confounding, including adjustment for other sex hormones. We then created more parsimonious final models by retaining only those variables that were significant at the P ⬍ .05 level in the full models for either men or women, in order to test for heterogeneity using the same model for both sexes. We also formally tested for interactions by sex using Wald tests. We performed sensitivity analyses to ensure that the estimates from the final regression model were robust to multiple conditions. Finally, we estimated the association between total testosterone and adiposity, in addition to the main models using bioavailable testosterone. Analyses were performed using Stata 11.
Results The final sample included 855 postmenopausal women and 936 men age 44 to 84 years at baseline. Women had significantly lower estradiol, bioavailable testosterone, DHEA, and visceral fat than men, but higher SHBG and subcutaneous fat (Supplemental Table 1). There were no differences in race/ethnicity. Figure 1 shows the unadjusted means and 95% confidence intervals of visceral fat and subcutaneous fat by sex-specific quintiles of estradiol, bioavailable testosterone, SHBG, and DHEA for women and men. Sex-specific hormone quintiles are given in Supplemental Table 2. For visceral fat (Figure 1A), there was a significant positive trend for estradiol, bioavailable testosterone, and DHEA, and a significant negative trend for SHBG in women. In men, higher quintiles of bioavailable testosterone, DHEA,
The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 20 February 2015. at 22:03 For personal use only. No other uses without permission. . All rights reserved.
doi: 10.1210/jc.2014-2934
and SHBG were significantly associated with lower mean visceral fat. All trends between visceral fat and sex hormones were significant at the P ⬍ .05 level, except for the estradiol relationship in men. For subcutaneous fat (Figure 1B), results were similar to those for visceral fat, except that the relationship with estradiol in men was significantly positive and no significant trend was seen for DHEA in either women or men. Table 1 and Supplemental Table 3 show results from the adjusted models, which gave broadly similar, but attenuated results to those shown in Figure 1. We detected no interactions by race/ethnicity. In the final models, we found a significant interaction by sex for bioavailable testosterone and DHEA, but not for estradiol or SHBG for both visceral and subcutaneous fat models. Estimates remained similar when adjusting for other hormones. We observed few changes in the estimates with subgroup analysis, with estimates in the same direction as those from the main analysis (Supplemental Table 4). Finally, visceral fat estimates for total testosterone were similar to those for bioavailable testosterone, even after adjusting for SHBG (data not shown).
Discussion In the MESA study, significant qualitative differences by sex, but not race/ethnicity, exist in the relationship between selected sex hormones and CT-measured body composition. In men, androgens were negatively related in varying degrees to fat in the visceral and subcutaneous
jcem.endojournals.org
E3
compartments. This association was reversed for women. In contrast, SHBG was inversely associated with fat from both compartments for both women and men. In women, there was a significant, but modest, positive association between estradiol and visceral fat, while for men this association was also positive, but not significantly different. Studies in men have shown the importance of testosterone in maintaining healthy body composition (11). While the evidence for testosterone is strongest for its association with lean muscle mass, testosterone has been shown to play a role in the deposition of fat to different body compartments (5). Most of the previous studies are consistent with our findings. Studies in men generally found an inverse association between testosterone and adiposity, as well as an inverse association between SHBG and adiposity (4, 12–16). Studies in women found a positive association between testosterone and adiposity, (6, 7, 17–20) but an inverse association between SHBG and adiposity (17, 19 –21). Studies investigating the association between estradiol and adiposity have produced inconsistent findings; (4, 6, 7, 12, 20) however, the two studies that investigated these relationships using CT or MRI to measure body composition found results somewhat similar to ours (4, 7). Despite increasing interest in the role that sex hormones play in body composition, studies that simultaneously investigate the associations of both estrogen and androgen are rare (6, 7, 12, 20). Similarly, studies on sex hormones have predominantly focused on the health of either women or men, but not both, limiting inference about
Figure 1. A. Unadjusted mean visceral fat area by sex-specific sex hormone quintiles. B. Unadjusted mean subcutaneous fat area by sex-specific hormone quintiles.
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E4
Sex hormones and adiposity
J Clin Endocrinol Metab
Table 1. Percent difference in back-transformed visceral fat (ln cm2) for every percent difference in backtransformed sex hormone (ln nmol/liter) in 1835 participants aged 45– 84 in the MESA Body Composition ancillary study Visceral Fat
Women
Men
P-value for Heterogeneity by Sex
Unadjusted Model Estradiol Bioavailable Testosterone SHBG DHEA
Estradiol Bioavailable Testosterone SHBG DHEA Final Model
5.02 (1.01 9.42)
6.08 (-1.98, 15.03) ⴚ9.51 (-15.63, ⫺2.96)
17.25 (12.75, 22.14) -25.92 (-29.53, ⫺22.12) -23.66 (-28.82, ⫺17.3) 6.72 (0.60, 12.75) -10.42 (-16.47, ⫺4.69) Adjusted for: race/ethnicity ⫹ age ⫹ income ⫹ education 8.22 (4.39, 11.63) 17.35 (12.75, 22.14) -27.39 (-30.93, ⫺23.66) 10.52 (4.08, 17.35)
0.83
