Clinical Medicine
The Journal of Clinical Investigation
Gonadal steroid–dependent effects on bone turnover and bone mineral density in men Joel S. Finkelstein,1 Hang Lee,2 Benjamin Z. Leder,1 Sherri-Ann M. Burnett-Bowie,1 David W. Goldstein,1 Christopher W. Hahn,1 Sarah C. Hirsch,1 Alex Linker,1 Nicholas Perros,1 Andrew B. Servais,1 Alexander P. Taylor,1 Matthew L. Webb,1 Jonathan M. Youngner,1 and Elaine W. Yu1 Endocrine Unit, Department of Medicine and 2Biostatistics Center, Massachusetts General Hospital, Boston, Massachusetts, USA.
1
BACKGROUND. Severe gonadal steroid deficiency induces bone loss in adult men; however, the specific roles of androgen and estrogen deficiency in hypogonadal bone loss are unclear. Additionally, the threshold levels of testosterone and estradiol that initiate bone loss are uncertain. METHODS. One hundred ninety-eight healthy men, ages 20–50, received goserelin acetate, which suppresses endogenous gonadal steroid production, and were randomized to treatment with 0, 1.25, 2.5, 5, or 10 grams of testosterone gel daily for 16 weeks. An additional cohort of 202 men was randomized to receive these treatments plus anastrozole, which suppresses conversion of androgens to estrogens. Thirty-seven men served as controls and received placebos for goserelin and testosterone. Changes in bone turnover markers, bone mineral density (BMD) by dual-energy x-ray absorptiometry (DXA), and BMD by quantitative computed tomography (QCT) were assessed in all men. Bone microarchitecture was assessed in 100 men. RESULTS. As testosterone dosage decreased, the percent change in C-telopeptide increased. These increases were considerably greater when aromatization of testosterone to estradiol was also suppressed, suggesting effects of both testosterone and estradiol deficiency. Decreases in DXA BMD were observed when aromatization was suppressed but were modest in most groups. QCT spine BMD fell substantially in all testosterone-dose groups in which aromatization was also suppressed, and this decline was independent of testosterone dose. Estradiol deficiency disrupted cortical microarchitecture at peripheral sites. Estradiol levels above 10 pg/ml and testosterone levels above 200 ng/dl were generally sufficient to prevent increases in bone resorption and decreases in BMD in men. CONCLUSIONS. Estrogens primarily regulate bone homeostasis in adult men, and testosterone and estradiol levels must decline substantially to impact the skeleton. TRIAL REGISTRATION. ClinicalTrials.gov, NCT00114114. FUNDING. AbbVie Inc., AstraZeneca Pharmaceuticals LP, NIH.
Introduction
Gonadal steroids have powerful effects on bone. During puberty, increases in gonadal steroids stimulate osteoblast activity, causing bone mineral density (BMD) to increase markedly (1). At midlife in women, gonadal steroids decline to prepubertal levels, which in turn increases bone resorption and leads to rapid bone loss (2). Unlike in women, decreases in gonadal steroids in middle-aged and elderly men are quite modest (3, 4). If adult men develop severe hypogonadism, however, as happens in men receiving gonadotropin-releasing hormone (GnRH) agonist therapy for prostate cancer, bone resorption increases and leads to rapid bone loss (5, 6). The levels to which gonadal steroids must be reduced
Role of the funding source: The sponsors of the study had no role in study design, data collection, data analysis, data interpretation, or drafting of the manuscript. Sponsors were allowed to review the manuscript to ensure proper acknowledgement of their support. Conflict of interest: The authors have declared that no conflict of interest exists. Submitted: August 14, 2015; Accepted: December 10, 2015. Reference information: J Clin Invest. 2016;126(3):1114–1125. doi:10.1172/JCI84137.
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to initiate bone loss in men are unknown, however. This issue is clinically important because male aging is associated with modest declines in both gonadal steroids and BMD (7), but it is not known whether those changes are causally related. Confirmation of causality and identification of thresholds below which skeletal effects are apparent would help to guide evidence-based decisions about testosterone replacement therapy in adult men. Over 80% of circulating estradiol in men is derived from aromatization of testosterone (8). Thus, serum testosterone and estradiol levels are correlated (9), and the prototypical changes in hypogonadal men — including alterations in body composition, decreases in sexual function, and high turnover bone loss — could be due to androgen deficiency, estrogen deficiency, or both (10). Several findings have been cited as evidence supporting a pivotal role of estrogen in adult male skeletal homeostasis (11). However, they do not definitively establish a causal role for estrogen deficiency in adult male hypogonadal bone loss. In this study, we utilized a variety of pharmacologic interventions to isolate the specific roles of androgens and estrogens in the pathogenesis of hypogonadal bone loss in
The Journal of Clinical Investigation
Clinical Medicine
Figure 1. Trial profile. T, testosterone gel. G, group. G1, 0 g (placebo) testosterone gel daily; G2, 1.25 g of testosterone daily; G3, 2.5 g of testosterone daily; G4, 5 g of testosterone gel daily; G5, 10 g of testosterone gel daily.
adult men and to determine the levels of testosterone and estradiol at which the risk of hypogonadal bone loss begins to increase.
Results
Baseline characteristics. Figure 1 shows details related to recruitment into each of the three cohorts, the randomization of subjects into each of the five testosterone-dose groups in cohorts 1 and 2, and the completion rates for each testosterone-dose group at each study visit. Table 1 shows the baseline characteristics of the three cohorts and Supplemental Table 1 (supplemental material available online with this article; doi:10.1172/JCI84137DS1) shows the self-reported race/ethnicity of the men in each cohort. There were no significant differences in baseline characteristics between the controls and any of the groups in cohorts 1 or 2. Other than a slightly higher mean baseline serum testosterone level in the men who dropped out early in cohort 1 (513 ± 135 vs. 569 ± 179 ng/dl, P < 0.05), there were no significant differences in baseline characteristics between the men who completed the protocol and those who discontinued participation before week 16 in any cohort. Reasons
for early discontinuation are summarized in Supplemental Table 2. Hormone levels. Figure 2 shows the mean serum testosterone and estradiol levels in relation to testosterone dose in each study group in cohort 1 (blue dots), cohort 2 (red dots), and the controls (black dots). Mean serum testosterone levels on therapy ranged from 44 ± 13 to 805 ± 355 ng/dl in cohort 1 and from 41 ± 13 to 924 ± 521 ng/dl in cohort 2. Mean serum estradiol levels ranged from 3.6 ± 1.4 to 33 ± 15 pg/ml in cohort 1 and from 1.0 ± 0.4 to 2.8 ± 1.8 pg/ml in cohort 2. Mean serum testosterone and estradiol levels were 591 ± 173 ng/dl and 29 ± 9 pg/ml in the controls. Serum testosterone and serum estradiol levels were highly correlated and best fit by a linear regression (E2 = 0.0356(T) + 4.4003; R = 0.79). Effects of testosterone dose and level on bone turnover markers. Figure 3 shows the percent change in serum C-terminal telopeptide of type 1 collagen (CTX) and procollagen type-1 amino-terminal propeptide (P1NP) in relation both to testosterone dose and to the mean serum testosterone levels during weeks 4–16 in men who received testosterone with (cohort 2) and without (cohort 1) coadministration of anastrozole. Within cohort 1 (blue dots), serum CTX levels increased jci.org Volume 126 Number 3 March 2016
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Clinical Medicine
The Journal of Clinical Investigation
Table 1. Mean (±SD) baseline values in each testosterone dose group in cohort 1 (top row of each pair) and cohort 2 (bottom row of each pair) and in controls
N (Cohort 1) N (Cohort 2) Age (years) Height (cm) Weight (kg) BMI (kg/m2) Testosterone (ng/dl) Estradiol (pg/ml) C-telopeptide (ng/ml) P1NP (ug/l)C DXA Spine BMD (g/cm2) DXA Total Hip BMD (g/cm2) DXA Total Body BMD (g/cm2) QCT Spine BMD (mg/cm3)
Group 1 0 g/day
Group 2 1.25 g/day
Group 3 2.5 g/day
Group 4 5 g/day
Group 5 10 g/day
41 38 32 + 9 34 + 7 179 + 6A 175 + 6 84 + 14 84 + 15 26 + 4 27 + 5 510 + 160 511 + 181 27 + 8B 32 + 10 0.37 + 0.16 0.37 + 0.19 56.2 + 24.2 49.0 + 11.6 1.08 + 0.14 1.09 + 0.16 1.07 + 0.15 1.07 + 0.16 1.15 + 0.11 1.14 + 0.13 146 + 31 140 + 27
41 38 34 + 7 33 + 7 177 + 6 177 + 6 84 + 14 87 + 17 27 + 4 28 + 5 506 + 154 548 + 189 27 + 8B 32 + 10 0.35 + 0.15 0.36 + 0.14 52.3 + 19.5 61.4 + 26.8 1.10 + 0.16 1.09 + 0.13 1.08 + 0.14 1.11 + 0.14 1.19 + 0.11 1.18 + 0.13 149 + 27 151 + 31
34 43 32 + 8 33 + 7 176 + 6 177 + 8 78 + 15 83 + 14 25 + 4 26 + 4 574 + 125 512 + 159 32 + 10 30 + 13 0.35 + 0.13 0.37 + 0.17 49.7 + 22.5 56.0 + 21.5 1.12 + 0.11 1.07 + 0.11 1.10 + 0.16 1.06 + 0.15 1.19 + 0.11 1.15 + 0.10 155 + 22 147 + 26
38 42 34 + 8 33 + 6 173 + 7B 176 + 7 78 + 14B 87 + 15 26 + 4 28 + 5 506 + 138 514 + 176 27 + 8 30 + 10 0.31 + 0.11 0.35 + 0.13 51.9 + 13.7 46.6 + 19.5 1.06 + 0.13 1.08 + 0.14 1.03 + 0.18 1.07 + 0.15 1.11 + 0.08 1.15 + 0.10 147 + 30 145 + 24
44 41 33 + 8 34 + 6 177 + 8 177 + 6 85 + 18 83 + 12 27 + 5 26 + 4 529 + 140 517 + 151 29 + 9 27 + 9 0.34 + 0.14 0.36 + 0.13 52.9 + 18.0 45.8 + 11.1 1.11 + 0.12 1.08 + 0.13 1.11 + 0.15 1.06 + 0.14 1.16 + 0.10 1.14 + 0.10 158 + 29 145 + 27
Controls (n = 37)
30 + 6 177 + 7 83 + 18 26 + 5 569 + 199 30 + 10 0.37 + 0.15 62.3 + 29.6 1.12 + 0.156 1.12 + 0.155 1.18+ 0.12 159 + 25
To convert testosterone to nmol/l, multiply by 0.03467. To convert estradiol to pmol/l, multiply by 3.671. AP
The Journal of Clinical Investigation
Gonadal steroid–dependent effects on bone turnover and bone mineral density in men Joel S. Finkelstein,1 Hang Lee,2 Benjamin Z. Leder,1 Sherri-Ann M. Burnett-Bowie,1 David W. Goldstein,1 Christopher W. Hahn,1 Sarah C. Hirsch,1 Alex Linker,1 Nicholas Perros,1 Andrew B. Servais,1 Alexander P. Taylor,1 Matthew L. Webb,1 Jonathan M. Youngner,1 and Elaine W. Yu1 Endocrine Unit, Department of Medicine and 2Biostatistics Center, Massachusetts General Hospital, Boston, Massachusetts, USA.
1
BACKGROUND. Severe gonadal steroid deficiency induces bone loss in adult men; however, the specific roles of androgen and estrogen deficiency in hypogonadal bone loss are unclear. Additionally, the threshold levels of testosterone and estradiol that initiate bone loss are uncertain. METHODS. One hundred ninety-eight healthy men, ages 20–50, received goserelin acetate, which suppresses endogenous gonadal steroid production, and were randomized to treatment with 0, 1.25, 2.5, 5, or 10 grams of testosterone gel daily for 16 weeks. An additional cohort of 202 men was randomized to receive these treatments plus anastrozole, which suppresses conversion of androgens to estrogens. Thirty-seven men served as controls and received placebos for goserelin and testosterone. Changes in bone turnover markers, bone mineral density (BMD) by dual-energy x-ray absorptiometry (DXA), and BMD by quantitative computed tomography (QCT) were assessed in all men. Bone microarchitecture was assessed in 100 men. RESULTS. As testosterone dosage decreased, the percent change in C-telopeptide increased. These increases were considerably greater when aromatization of testosterone to estradiol was also suppressed, suggesting effects of both testosterone and estradiol deficiency. Decreases in DXA BMD were observed when aromatization was suppressed but were modest in most groups. QCT spine BMD fell substantially in all testosterone-dose groups in which aromatization was also suppressed, and this decline was independent of testosterone dose. Estradiol deficiency disrupted cortical microarchitecture at peripheral sites. Estradiol levels above 10 pg/ml and testosterone levels above 200 ng/dl were generally sufficient to prevent increases in bone resorption and decreases in BMD in men. CONCLUSIONS. Estrogens primarily regulate bone homeostasis in adult men, and testosterone and estradiol levels must decline substantially to impact the skeleton. TRIAL REGISTRATION. ClinicalTrials.gov, NCT00114114. FUNDING. AbbVie Inc., AstraZeneca Pharmaceuticals LP, NIH.
Introduction
Gonadal steroids have powerful effects on bone. During puberty, increases in gonadal steroids stimulate osteoblast activity, causing bone mineral density (BMD) to increase markedly (1). At midlife in women, gonadal steroids decline to prepubertal levels, which in turn increases bone resorption and leads to rapid bone loss (2). Unlike in women, decreases in gonadal steroids in middle-aged and elderly men are quite modest (3, 4). If adult men develop severe hypogonadism, however, as happens in men receiving gonadotropin-releasing hormone (GnRH) agonist therapy for prostate cancer, bone resorption increases and leads to rapid bone loss (5, 6). The levels to which gonadal steroids must be reduced
Role of the funding source: The sponsors of the study had no role in study design, data collection, data analysis, data interpretation, or drafting of the manuscript. Sponsors were allowed to review the manuscript to ensure proper acknowledgement of their support. Conflict of interest: The authors have declared that no conflict of interest exists. Submitted: August 14, 2015; Accepted: December 10, 2015. Reference information: J Clin Invest. 2016;126(3):1114–1125. doi:10.1172/JCI84137.
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jci.org Volume 126 Number 3 March 2016
to initiate bone loss in men are unknown, however. This issue is clinically important because male aging is associated with modest declines in both gonadal steroids and BMD (7), but it is not known whether those changes are causally related. Confirmation of causality and identification of thresholds below which skeletal effects are apparent would help to guide evidence-based decisions about testosterone replacement therapy in adult men. Over 80% of circulating estradiol in men is derived from aromatization of testosterone (8). Thus, serum testosterone and estradiol levels are correlated (9), and the prototypical changes in hypogonadal men — including alterations in body composition, decreases in sexual function, and high turnover bone loss — could be due to androgen deficiency, estrogen deficiency, or both (10). Several findings have been cited as evidence supporting a pivotal role of estrogen in adult male skeletal homeostasis (11). However, they do not definitively establish a causal role for estrogen deficiency in adult male hypogonadal bone loss. In this study, we utilized a variety of pharmacologic interventions to isolate the specific roles of androgens and estrogens in the pathogenesis of hypogonadal bone loss in
The Journal of Clinical Investigation
Clinical Medicine
Figure 1. Trial profile. T, testosterone gel. G, group. G1, 0 g (placebo) testosterone gel daily; G2, 1.25 g of testosterone daily; G3, 2.5 g of testosterone daily; G4, 5 g of testosterone gel daily; G5, 10 g of testosterone gel daily.
adult men and to determine the levels of testosterone and estradiol at which the risk of hypogonadal bone loss begins to increase.
Results
Baseline characteristics. Figure 1 shows details related to recruitment into each of the three cohorts, the randomization of subjects into each of the five testosterone-dose groups in cohorts 1 and 2, and the completion rates for each testosterone-dose group at each study visit. Table 1 shows the baseline characteristics of the three cohorts and Supplemental Table 1 (supplemental material available online with this article; doi:10.1172/JCI84137DS1) shows the self-reported race/ethnicity of the men in each cohort. There were no significant differences in baseline characteristics between the controls and any of the groups in cohorts 1 or 2. Other than a slightly higher mean baseline serum testosterone level in the men who dropped out early in cohort 1 (513 ± 135 vs. 569 ± 179 ng/dl, P < 0.05), there were no significant differences in baseline characteristics between the men who completed the protocol and those who discontinued participation before week 16 in any cohort. Reasons
for early discontinuation are summarized in Supplemental Table 2. Hormone levels. Figure 2 shows the mean serum testosterone and estradiol levels in relation to testosterone dose in each study group in cohort 1 (blue dots), cohort 2 (red dots), and the controls (black dots). Mean serum testosterone levels on therapy ranged from 44 ± 13 to 805 ± 355 ng/dl in cohort 1 and from 41 ± 13 to 924 ± 521 ng/dl in cohort 2. Mean serum estradiol levels ranged from 3.6 ± 1.4 to 33 ± 15 pg/ml in cohort 1 and from 1.0 ± 0.4 to 2.8 ± 1.8 pg/ml in cohort 2. Mean serum testosterone and estradiol levels were 591 ± 173 ng/dl and 29 ± 9 pg/ml in the controls. Serum testosterone and serum estradiol levels were highly correlated and best fit by a linear regression (E2 = 0.0356(T) + 4.4003; R = 0.79). Effects of testosterone dose and level on bone turnover markers. Figure 3 shows the percent change in serum C-terminal telopeptide of type 1 collagen (CTX) and procollagen type-1 amino-terminal propeptide (P1NP) in relation both to testosterone dose and to the mean serum testosterone levels during weeks 4–16 in men who received testosterone with (cohort 2) and without (cohort 1) coadministration of anastrozole. Within cohort 1 (blue dots), serum CTX levels increased jci.org Volume 126 Number 3 March 2016
1115
Clinical Medicine
The Journal of Clinical Investigation
Table 1. Mean (±SD) baseline values in each testosterone dose group in cohort 1 (top row of each pair) and cohort 2 (bottom row of each pair) and in controls
N (Cohort 1) N (Cohort 2) Age (years) Height (cm) Weight (kg) BMI (kg/m2) Testosterone (ng/dl) Estradiol (pg/ml) C-telopeptide (ng/ml) P1NP (ug/l)C DXA Spine BMD (g/cm2) DXA Total Hip BMD (g/cm2) DXA Total Body BMD (g/cm2) QCT Spine BMD (mg/cm3)
Group 1 0 g/day
Group 2 1.25 g/day
Group 3 2.5 g/day
Group 4 5 g/day
Group 5 10 g/day
41 38 32 + 9 34 + 7 179 + 6A 175 + 6 84 + 14 84 + 15 26 + 4 27 + 5 510 + 160 511 + 181 27 + 8B 32 + 10 0.37 + 0.16 0.37 + 0.19 56.2 + 24.2 49.0 + 11.6 1.08 + 0.14 1.09 + 0.16 1.07 + 0.15 1.07 + 0.16 1.15 + 0.11 1.14 + 0.13 146 + 31 140 + 27
41 38 34 + 7 33 + 7 177 + 6 177 + 6 84 + 14 87 + 17 27 + 4 28 + 5 506 + 154 548 + 189 27 + 8B 32 + 10 0.35 + 0.15 0.36 + 0.14 52.3 + 19.5 61.4 + 26.8 1.10 + 0.16 1.09 + 0.13 1.08 + 0.14 1.11 + 0.14 1.19 + 0.11 1.18 + 0.13 149 + 27 151 + 31
34 43 32 + 8 33 + 7 176 + 6 177 + 8 78 + 15 83 + 14 25 + 4 26 + 4 574 + 125 512 + 159 32 + 10 30 + 13 0.35 + 0.13 0.37 + 0.17 49.7 + 22.5 56.0 + 21.5 1.12 + 0.11 1.07 + 0.11 1.10 + 0.16 1.06 + 0.15 1.19 + 0.11 1.15 + 0.10 155 + 22 147 + 26
38 42 34 + 8 33 + 6 173 + 7B 176 + 7 78 + 14B 87 + 15 26 + 4 28 + 5 506 + 138 514 + 176 27 + 8 30 + 10 0.31 + 0.11 0.35 + 0.13 51.9 + 13.7 46.6 + 19.5 1.06 + 0.13 1.08 + 0.14 1.03 + 0.18 1.07 + 0.15 1.11 + 0.08 1.15 + 0.10 147 + 30 145 + 24
44 41 33 + 8 34 + 6 177 + 8 177 + 6 85 + 18 83 + 12 27 + 5 26 + 4 529 + 140 517 + 151 29 + 9 27 + 9 0.34 + 0.14 0.36 + 0.13 52.9 + 18.0 45.8 + 11.1 1.11 + 0.12 1.08 + 0.13 1.11 + 0.15 1.06 + 0.14 1.16 + 0.10 1.14 + 0.10 158 + 29 145 + 27
Controls (n = 37)
30 + 6 177 + 7 83 + 18 26 + 5 569 + 199 30 + 10 0.37 + 0.15 62.3 + 29.6 1.12 + 0.156 1.12 + 0.155 1.18+ 0.12 159 + 25
To convert testosterone to nmol/l, multiply by 0.03467. To convert estradiol to pmol/l, multiply by 3.671. AP
