madman
Super Moderator
Effects of estradiol on fat in men undergoing androgen deprivation therapy: a randomized trial (2022)
Nicholas Russell, Rudolf Hoermann, Ada S Cheung, Jeffrey D Zajac, David J Handelsman and Mathis Grossmann
Abstract
Objective: Indirect evidence suggests that the effects of testosterone on fat mass in men are dependent on aromatization to estradiol (E2). However, no controlled study has assessed the effects of E2 in the absence of testosterone.
Design: Six-month randomized, placebo-controlled trial with the hypothesis that men randomized to E2 would reduce their fat mass.
Methods: Seventy-eight participants receiving androgen deprivation therapy for prostate cancer were randomized to 0.9 mg of 0.1% E2 gel per day, or matched placebo. Dual x-ray absorptiometry body composition was measured at baseline, month 3, and month 6. The primary outcome was total fat mass.
Results: Serum E2 increased in the estradiol group over 6 months compared to placebo, and the mean-adjusted difference (MAD) was 207 pmol/L (95% CI: 123–292), P < 0.001. E2 treatment changed total fat mass, MAD 1007 g (95% CI: 124–1891), but not significantly, so P = 0.09. There were other consistent non-significant trends toward increased proportional fat mass, MAD 0.8% (95% CI: 0.0–1.6), P= 0.15; gynoid fat, MAD 147 g (95% CI: 2–293), P = 0.08; visceral fat, 53 g (95% CI: 1–105) P = 0.13; and subcutaneous fat, MAD 65 g (95% CI: 5–125), P = 0.11. Android fat increased, MAD 164 g (95% CI: 41–286), P = 0.04.
Conclusion: Contrary to our hypothesis, we provide suggestive evidence that E2 acting in the absence of testosterone, may increase total and regional fat mass in men. Given the premature closure of clinical trials due to the COVID pandemic, this potentially important observation should encourage additional studies to confirm or refute whether E2 promotes fat expansion in the absence of testosterone.
Introduction
Exogenous testosterone administration reduces fat mass in hypogonadal men (1, 2, 3) and in older men with age-associated low serum testosterone (4, 5). By comparison, aromatase inhibitors, which increase serum testosterone and reduce estradiol (E2), do not decrease fat mass in older men with low testosterone (6) raising the question of whether the effect of testosterone on fat mass is aromatization-dependent (7). Supporting this concept are observations that men with germline loss of function of the estrogen receptor-alpha (ER-alpha) (8) or aromatase (9) genes display excess adiposity and insulin resistance, and experimental data suggesting that intact aromatization is required to prevent fat gain induced by short-term hypogonadism (10, 11). In women, E2 replacement reduces the postmenopausal accumulation of central fat (12). However, the hypothesis that E2 prevents fat accumulation in men, independently of testosterone, has not been tested experimentally by investigating E2 actions in the absence of testosterone.
Mouse studies are generally supportive of the notion that the regulatory effects of testosterone on fat mass in adult males are, at least in part, dependent on the actions of E2. The male global ER-alpha knockout mouse displays the age-dependent accumulation of white adipose tissue due to an increase in adipocyte size and number that is not due to increased food consumption, but rather lower overall energy expenditure (13, 14). Male aromatase knockout mice (15) display a similar phenotype. Tissue-specific knockout models have highlighted direct and indirect effects for E2 acting on ER-alpha in adipose tissue, brain, and possibly skeletal muscle in preventing fat accumulation and inflammation but also that E2 acting via ER-alpha is necessary for proliferation and differentiation of pre-adipocytes during development (16). Experiments in orchiectomized adult male mice have shown that E2 is important in the prevention of fat accumulation, possibly with a visceral depot-specific effect (17, 18, 19).
Androgen deprivation therapy (ADT) for prostate cancer is the most frequent contemporary cause of severe sex steroid deficiency in older men, with serum testosterone and its substrate E2 circulating at near castrate concentrations (20). Medical castration is used for up to 3 years in the adjuvant setting in combination with curative-intent radiotherapy, and as palliative treatment for metastatic disease (21, 22). ADT is usually achieved by administration of gonadotropin-releasing hormone (GnRH) analogs, representing the only clinical situation where standard clinical care allows for the prolonged deferral of testosterone replacement. This creates the opportunity for the isolated effect of E2 to be observed in the absence of testosterone.
Men commencing ADT typically gain fat mass and lose lean mass. In a meta-analysis of seven uncontrolled observational studies (325 participants), ranging in duration from 3 to12 months, the pooled estimate of mean change in fat mass by dual x-ray absorptiometry (DXA) was 7.7% (95% CI: 4.3–11.2%, P < 0.0001) (23). In six studies (260 participants), mean change in lean mass was −2.8% (95% CI: −3.6 to −2.0%), P < 0.00001 (15). In a controlled experiment enrolling healthy older male volunteers, 16-weeks of ADT increased fat mass by 12% and reduced lean mass by 2% (3).
*In this trial, we aimed to assess the effect of transdermal E2 on fat mass over 6 months in men undergoing medical castration with ADT. The E2 dose was selected to target a minimum circulating E2 concentration in the range present in eugonadal men (E2 ‘add-back’). We hypothesized that men randomized to E2 add-back, compared to those randomized to placebo, would reduce their fat mass.
Subjects and methods
We conducted a 6-month, randomized, double-blinded, placebo-controlled, parallel-group trial at Austin Health, a tertiary referral hospital affiliated with The University of Melbourne. Participants were recruited from outpatient clinics from November 2017 to February 2020 until recruitment was terminated prematurely due to the COVID-19 pandemic. Men were eligible for the study if they had been receiving GnRH agonists or antagonists for prostate cancer for a minimum of 4 weeks, with that therapy intended to continue for at least a further of 6 months. Exclusion criteria were impaired performance status (Eastern Cooperative Oncology Group Performance Status (ECOG) >2); bone metastases at scanning sites; history of venous thromboembolism (VTE); breast cancer; prior antiresorptive or strontium ranelate use or current indication for such therapy; systolic blood pressure >160 or diastolic blood pressure >100; New York Heart Association class 3 or 4 angina or heart failure; stroke, transient ischaemic attack, myocardial infarction, or angina within 12 months; current oral glucocorticoid treatment; prior chemotherapy; and alcohol or illicit drug abuse.
The trial protocol was approved by the Austin Health Human Research Ethics Committee (HREC/16/Austin/98) and each participant provided written informed consent. The trial was preregistered with the Australian New Zealand Clinical Trials Registry (identifier 12614000689673). We followed the Consolidated Standards of Reporting Trials checklist in reporting this randomized trial (24).
Participants were randomly allocated, in a concealed fashion by clinical pharmacists independent of trial investigators, to two intervention groups: E2 gel 1 mL (0.9 mg) per day or matching placebo gel 1 mL per day. We previously observed that E2 gel 0.9 mg daily increased the minimum serum E2 of men undergoing ADT into the reference range for healthy older men (25). Randomization occurred as follows: First, participants were stratified by ADT duration (≤3 or >3 months) and then by eligibility to undergo brain MRI (data to be reported separately). Secondly, participants were allocated by restricted randomization, using a computer-generated randomization scheme in blocks of size 4, to E2 or placebo in a ratio of 1:1.
E2 gel was Sandrena™ 1 mg/g E2 (Aspen Pharmacare, St Leonards, Australia). Placebo gel was a-gel™ (Fresenius Kabi, North Ryde, Australia) and matched the E2 gel for color, smell, and consistency. E2 and placebo were re-packaged into identical 10 mL syringes by pharmacy, with instructions to apply 1 mL each morning to the skin of the upper arms or abdomen. The concealed treatment allocation maintained the blinding of participants, investigators, and clinicians during treatment, with blinding maintained until data analysis, after the database had been cleaned and locked. Used syringes were retrieved to calculate gel usage.
Study visits were conducted at baseline, month 1, month 3, and month 6 of the intervention. Gel syringes were collected during each visit and residual volume was recorded to assess adherence. Adverse events were graded according to Common Terminology Criteria for Adverse Events (CTCAE) version 4.03 (26).
Self-reported time spent performing weight-bearing exercise was recorded at baseline and average daily step count and proportion of awake time spent doing non-sedentary activity were measured for 1 week at baseline and 6 months by accelerometer (GT3x, Actigraph, Pensacola, USA). Participants were given standard advice at baseline and throughout the study encouraging regular cardiovascular and resistance exercise.
Discussion
In this randomized controlled trial (RCT), we aimed to assess the effect of E2 add-back on fat mass in men rendered castrate by ADT for prostate cancer. Contrary to our hypothesis, E2 did not reduce fat mass over 6 months. On the contrary, while not statistically significant, we observed a consistent trend in the opposite direction on several measures of body fat. Men assigned to E2, compared to placebo, demonstrated trends toward increased total fat mass with a pattern of concordant trends in regional android fat, gynoid fat, VAT, and SAT mass which all had positive 95% CIs at 6 months and overall P values around 0.1.
*In this trial, we refute the hypothesis of a fat-decreasing effect of E2 add-back in men on ADT. E2 also did not lower HOMA2-IR as hypothesized, and it did not have the expected effect to lower HDL-C. Unexpectedly, E2 add-back fell short of significantly lowering IGF-1 and raising SHBG, over placebo, although the 95% CIs at 6 months were suggestive of such effects. One reason for failing to confirm our primary hypothesis could have been insufficient target organ estrogenization. However, E2 did produce expected (adverse) effects at the breast, and significantly reduced bone resorption as determined by measuring serum beta carboxyl-terminal type 1 collagen telopeptide (bone data to be reported separately). Premature closure of the study to the COVID-19 pandemic is another possible explanation for these findings.
Significance and conclusions
The unique experimental design of this study allowed us to examine the effects of E2 on male fat mass in the absence of testosterone. We refute our hypothesis of a direct E2 effect to reduce fat mass but provide suggestive evidence that, contrary to our hypothesis, E2, without testosterone, may increase, rather than decrease total and regional fat mass over 6 months. While preliminary, these findings provide insights into biological actions of E2 in men, which may be more complex than traditionally assumed. While work by Finkelstein et al., and others, discussed above, has highlighted the importance of E2 in determining fat distribution and accumulation in combination with testosterone replacement, this RCT suggests E2 might be permissive for actions of androgens in preventing fat accumulation but that E2 itself is not solely responsible for these effects. This insight, if confirmed would be relevant for designing optimal hormone replacement regimens for hypogonadal men. Moreover, E2, albeit in higher doses, is currently under investigation as a sole mode of ADT (59). Given that E2 as a sole mode of ADT reduces testosterone to castrate concentrations, a better understanding of the effects of E2 on fat mass and cardiometabolic risk factors has clinical relevance, particularly since cardiovascular events are a common cause of death in men with early prostate cancer.
Nicholas Russell, Rudolf Hoermann, Ada S Cheung, Jeffrey D Zajac, David J Handelsman and Mathis Grossmann
Abstract
Objective: Indirect evidence suggests that the effects of testosterone on fat mass in men are dependent on aromatization to estradiol (E2). However, no controlled study has assessed the effects of E2 in the absence of testosterone.
Design: Six-month randomized, placebo-controlled trial with the hypothesis that men randomized to E2 would reduce their fat mass.
Methods: Seventy-eight participants receiving androgen deprivation therapy for prostate cancer were randomized to 0.9 mg of 0.1% E2 gel per day, or matched placebo. Dual x-ray absorptiometry body composition was measured at baseline, month 3, and month 6. The primary outcome was total fat mass.
Results: Serum E2 increased in the estradiol group over 6 months compared to placebo, and the mean-adjusted difference (MAD) was 207 pmol/L (95% CI: 123–292), P < 0.001. E2 treatment changed total fat mass, MAD 1007 g (95% CI: 124–1891), but not significantly, so P = 0.09. There were other consistent non-significant trends toward increased proportional fat mass, MAD 0.8% (95% CI: 0.0–1.6), P= 0.15; gynoid fat, MAD 147 g (95% CI: 2–293), P = 0.08; visceral fat, 53 g (95% CI: 1–105) P = 0.13; and subcutaneous fat, MAD 65 g (95% CI: 5–125), P = 0.11. Android fat increased, MAD 164 g (95% CI: 41–286), P = 0.04.
Conclusion: Contrary to our hypothesis, we provide suggestive evidence that E2 acting in the absence of testosterone, may increase total and regional fat mass in men. Given the premature closure of clinical trials due to the COVID pandemic, this potentially important observation should encourage additional studies to confirm or refute whether E2 promotes fat expansion in the absence of testosterone.
Introduction
Exogenous testosterone administration reduces fat mass in hypogonadal men (1, 2, 3) and in older men with age-associated low serum testosterone (4, 5). By comparison, aromatase inhibitors, which increase serum testosterone and reduce estradiol (E2), do not decrease fat mass in older men with low testosterone (6) raising the question of whether the effect of testosterone on fat mass is aromatization-dependent (7). Supporting this concept are observations that men with germline loss of function of the estrogen receptor-alpha (ER-alpha) (8) or aromatase (9) genes display excess adiposity and insulin resistance, and experimental data suggesting that intact aromatization is required to prevent fat gain induced by short-term hypogonadism (10, 11). In women, E2 replacement reduces the postmenopausal accumulation of central fat (12). However, the hypothesis that E2 prevents fat accumulation in men, independently of testosterone, has not been tested experimentally by investigating E2 actions in the absence of testosterone.
Mouse studies are generally supportive of the notion that the regulatory effects of testosterone on fat mass in adult males are, at least in part, dependent on the actions of E2. The male global ER-alpha knockout mouse displays the age-dependent accumulation of white adipose tissue due to an increase in adipocyte size and number that is not due to increased food consumption, but rather lower overall energy expenditure (13, 14). Male aromatase knockout mice (15) display a similar phenotype. Tissue-specific knockout models have highlighted direct and indirect effects for E2 acting on ER-alpha in adipose tissue, brain, and possibly skeletal muscle in preventing fat accumulation and inflammation but also that E2 acting via ER-alpha is necessary for proliferation and differentiation of pre-adipocytes during development (16). Experiments in orchiectomized adult male mice have shown that E2 is important in the prevention of fat accumulation, possibly with a visceral depot-specific effect (17, 18, 19).
Androgen deprivation therapy (ADT) for prostate cancer is the most frequent contemporary cause of severe sex steroid deficiency in older men, with serum testosterone and its substrate E2 circulating at near castrate concentrations (20). Medical castration is used for up to 3 years in the adjuvant setting in combination with curative-intent radiotherapy, and as palliative treatment for metastatic disease (21, 22). ADT is usually achieved by administration of gonadotropin-releasing hormone (GnRH) analogs, representing the only clinical situation where standard clinical care allows for the prolonged deferral of testosterone replacement. This creates the opportunity for the isolated effect of E2 to be observed in the absence of testosterone.
Men commencing ADT typically gain fat mass and lose lean mass. In a meta-analysis of seven uncontrolled observational studies (325 participants), ranging in duration from 3 to12 months, the pooled estimate of mean change in fat mass by dual x-ray absorptiometry (DXA) was 7.7% (95% CI: 4.3–11.2%, P < 0.0001) (23). In six studies (260 participants), mean change in lean mass was −2.8% (95% CI: −3.6 to −2.0%), P < 0.00001 (15). In a controlled experiment enrolling healthy older male volunteers, 16-weeks of ADT increased fat mass by 12% and reduced lean mass by 2% (3).
*In this trial, we aimed to assess the effect of transdermal E2 on fat mass over 6 months in men undergoing medical castration with ADT. The E2 dose was selected to target a minimum circulating E2 concentration in the range present in eugonadal men (E2 ‘add-back’). We hypothesized that men randomized to E2 add-back, compared to those randomized to placebo, would reduce their fat mass.
Subjects and methods
We conducted a 6-month, randomized, double-blinded, placebo-controlled, parallel-group trial at Austin Health, a tertiary referral hospital affiliated with The University of Melbourne. Participants were recruited from outpatient clinics from November 2017 to February 2020 until recruitment was terminated prematurely due to the COVID-19 pandemic. Men were eligible for the study if they had been receiving GnRH agonists or antagonists for prostate cancer for a minimum of 4 weeks, with that therapy intended to continue for at least a further of 6 months. Exclusion criteria were impaired performance status (Eastern Cooperative Oncology Group Performance Status (ECOG) >2); bone metastases at scanning sites; history of venous thromboembolism (VTE); breast cancer; prior antiresorptive or strontium ranelate use or current indication for such therapy; systolic blood pressure >160 or diastolic blood pressure >100; New York Heart Association class 3 or 4 angina or heart failure; stroke, transient ischaemic attack, myocardial infarction, or angina within 12 months; current oral glucocorticoid treatment; prior chemotherapy; and alcohol or illicit drug abuse.
The trial protocol was approved by the Austin Health Human Research Ethics Committee (HREC/16/Austin/98) and each participant provided written informed consent. The trial was preregistered with the Australian New Zealand Clinical Trials Registry (identifier 12614000689673). We followed the Consolidated Standards of Reporting Trials checklist in reporting this randomized trial (24).
Participants were randomly allocated, in a concealed fashion by clinical pharmacists independent of trial investigators, to two intervention groups: E2 gel 1 mL (0.9 mg) per day or matching placebo gel 1 mL per day. We previously observed that E2 gel 0.9 mg daily increased the minimum serum E2 of men undergoing ADT into the reference range for healthy older men (25). Randomization occurred as follows: First, participants were stratified by ADT duration (≤3 or >3 months) and then by eligibility to undergo brain MRI (data to be reported separately). Secondly, participants were allocated by restricted randomization, using a computer-generated randomization scheme in blocks of size 4, to E2 or placebo in a ratio of 1:1.
E2 gel was Sandrena™ 1 mg/g E2 (Aspen Pharmacare, St Leonards, Australia). Placebo gel was a-gel™ (Fresenius Kabi, North Ryde, Australia) and matched the E2 gel for color, smell, and consistency. E2 and placebo were re-packaged into identical 10 mL syringes by pharmacy, with instructions to apply 1 mL each morning to the skin of the upper arms or abdomen. The concealed treatment allocation maintained the blinding of participants, investigators, and clinicians during treatment, with blinding maintained until data analysis, after the database had been cleaned and locked. Used syringes were retrieved to calculate gel usage.
Study visits were conducted at baseline, month 1, month 3, and month 6 of the intervention. Gel syringes were collected during each visit and residual volume was recorded to assess adherence. Adverse events were graded according to Common Terminology Criteria for Adverse Events (CTCAE) version 4.03 (26).
Self-reported time spent performing weight-bearing exercise was recorded at baseline and average daily step count and proportion of awake time spent doing non-sedentary activity were measured for 1 week at baseline and 6 months by accelerometer (GT3x, Actigraph, Pensacola, USA). Participants were given standard advice at baseline and throughout the study encouraging regular cardiovascular and resistance exercise.
Discussion
In this randomized controlled trial (RCT), we aimed to assess the effect of E2 add-back on fat mass in men rendered castrate by ADT for prostate cancer. Contrary to our hypothesis, E2 did not reduce fat mass over 6 months. On the contrary, while not statistically significant, we observed a consistent trend in the opposite direction on several measures of body fat. Men assigned to E2, compared to placebo, demonstrated trends toward increased total fat mass with a pattern of concordant trends in regional android fat, gynoid fat, VAT, and SAT mass which all had positive 95% CIs at 6 months and overall P values around 0.1.
*In this trial, we refute the hypothesis of a fat-decreasing effect of E2 add-back in men on ADT. E2 also did not lower HOMA2-IR as hypothesized, and it did not have the expected effect to lower HDL-C. Unexpectedly, E2 add-back fell short of significantly lowering IGF-1 and raising SHBG, over placebo, although the 95% CIs at 6 months were suggestive of such effects. One reason for failing to confirm our primary hypothesis could have been insufficient target organ estrogenization. However, E2 did produce expected (adverse) effects at the breast, and significantly reduced bone resorption as determined by measuring serum beta carboxyl-terminal type 1 collagen telopeptide (bone data to be reported separately). Premature closure of the study to the COVID-19 pandemic is another possible explanation for these findings.
Significance and conclusions
The unique experimental design of this study allowed us to examine the effects of E2 on male fat mass in the absence of testosterone. We refute our hypothesis of a direct E2 effect to reduce fat mass but provide suggestive evidence that, contrary to our hypothesis, E2, without testosterone, may increase, rather than decrease total and regional fat mass over 6 months. While preliminary, these findings provide insights into biological actions of E2 in men, which may be more complex than traditionally assumed. While work by Finkelstein et al., and others, discussed above, has highlighted the importance of E2 in determining fat distribution and accumulation in combination with testosterone replacement, this RCT suggests E2 might be permissive for actions of androgens in preventing fat accumulation but that E2 itself is not solely responsible for these effects. This insight, if confirmed would be relevant for designing optimal hormone replacement regimens for hypogonadal men. Moreover, E2, albeit in higher doses, is currently under investigation as a sole mode of ADT (59). Given that E2 as a sole mode of ADT reduces testosterone to castrate concentrations, a better understanding of the effects of E2 on fat mass and cardiometabolic risk factors has clinical relevance, particularly since cardiovascular events are a common cause of death in men with early prostate cancer.
