0021-972x/92/7402-0332$03.00/0 Journal of Clinical Endocrinology and Metabolism Copyright 0 1992 by The Endocrine Society
Vol. 74, No. 2 Printed
in U.S.A.
Effect of Testosterone on Metabolic Rate and Body Composition in Normal Men and Men with Muscular Dystrophy* STEPHEN WELLE, RALPH AND ROBERT C. GRIGGS
JOZEFOWICZ,
GILBERT
FORBES,
Departments of Medicine, Neurology, and Pediatrics, Monroe Community Rochester School of Medicine and Dentistry, Rochester, New York 14620
ABSTRACT. We have examined the effect of testosterone enanthate injections (3 mg/kg. week, im) on the basal metabolic rate (BMR) estimated by indirect calorimetry and on lean body mass (LBM) estimated by “‘K counting in four normal men and nine men with muscular dystrophy. Testosterone treatment increased plasma testosterone levels in all subjects (3-fold mean elevation). BMR increased significantly after 3 months of testosterone treatment (mean, 10%; P < 0.01; 13% mean increase in the men with muscular dystrophy and 7% mean increase in the normal subjects). BMR remained elevated (mean increase, 9%) after 12 months of testosterone treatment in four men with muscular dystrophy. LBM also was significantly higher after 3 months of treatment (mean, 10%; P < 0.01) and remained elevated at 12 months. The percent increase in LBM was similar in men with muscular dystrophy (+lO%) and normal men
E
and the University
of
(+ll%). When BMR was adjusted for the increase in LBM by linear regression, the men with muscular dystrophy had an increase in adjusted BMR after 3 months of testosterone treatment (mean increase, 7%), but not after 12 months. The normal men did not have an increase in adjusted BMR. Testosterone treatment for 12 months slightly reduced body fat, whereas there was an increase in body fat in subjects with muscular dystrophy who were treated with placebo for 12 months. We conclude that there is a significant increase in BMR associated with pharmacological testosterone treatment, which for the most part is explained by the increase in LBM. However, in men with muscular dystrophy, there is a small hypermetabolic effect of testosterone beyond that explained by increased LBM. (J Clin Endocrinol Metub 74: 332-335, 1992)
studies of testosterone treatment demonstrated a 5-60% increase in BMR in hypogonadal
ARLY
Because BMR is the largest component of total energy expenditure, an increase in BMR could conceivably produce negative energy balance and reduce body fat.
men (l-3), but did not investigate the mechanism of this effect. Short term (7- to lo-day) administration of testosterone to eugonadal subjects did not increase the basal metabolic rate (BMR) (4,5). No systematic study of the effect of testosterone on metabolic rate in humans has been reported since these early findings. Thus, we have examined the effect of testosterone on BMR in subjects receiving pharmacological doses of testosterone for 3 months or longer. These studies addressed the hypothesis that an increase in BMR induced by testosterone could be explained by increased active cell mass, rather than a direct effect on energy metabolism. We were particularly interested in the effect of testosterone on BMR in sub-
jects with myotonic dystrophy,
Hospital,
Subjects
and Methods
Thirteen men, 18-45 yr old, were studied before and after a S-month period of testosterone administration. Nine of the subjects (seven with myotonic dystrophy, one with limb girdle dystrophy, and one with facioscapulohumeral dystrophy) were participating in therapeutic trials of testosterone. Four of the subjects were normal volunteers. Four of the subjects with myotonic dystrophy were also studied after 12 months of testosterone treatment. We also studied a control group comprised of five men with myotonic dystrophy treated with placebo for 12 months and three normal men whose BMR and lean body mass (LBM) measurements were repeated after a 3-month interval with no interventions. Mean ages, weights, baseline BMRs, and LBMs of each group are given in Table 1. Written and verbal informed consent was obtained from all subjects after the protocol was approved by the University of Rochester Research Subjects Review Board. BMR, LBM, 24-h urinary creatinine excretion (an index of muscle mass), and plasma levels of testosterone were measured before and after 3 months of treatment in all subjects, except
who have a high body fat
content even though total body weight is usually normal. Received April 10, 1991. Address all correspondence and requests for reprints to: Stephen Welle, Monroe Community Hospital, 435 East Henrietta Road, Endocrine Unit, Room 3C-22, Rochester, New York 14620. * This work was supported by grants from the NIH (N&22099, DK39063, HD-18454, and RR-00044) and the Muscular Dystrophy Association. 332
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TESTOSTERONE
AND METABOLIC
TABLE 1. Baseline weight, LBM, fat, and BMR Age W Testosterone-treated subjects Normal (n = 4) Muscular dystrophy (n = 9) Control subjects Normal (n = 3) Muscular dystrophy (n = 5)
Wt (kg)
LBM (kg)
Fat 04
BMR
&J/h)
33*3 73+5 62+2 llf4 304+23 32 f 3 69 + 5 47 + 3 22 + 5 251 + 13 22 + 1 72 + 1 62 f2 lo+ 2 286+ 5 34 + 4 70 f 5 47 + 5 23 + 8 249 + 20
Values are the mean + SEM.
that the three untreated normal volunteers had measurements of only BMR and LBM. The same variables were measured after 12 months in the placebo- and testosterone-treated subjects who participated in the longer protocol. Testosterone was administered weekly by a nurse as testosterone enanthate (3 mg/kg, im). BMR was measured after an overnight fast in the Clinical Research Center (CRC), using a ventilated mask indirect calorimetry method with a coefficient of variation (within days and between days) of less than 5% (6). LBM was determined by 40K counting, which has a coefficient of variation of 3% (7). Urinary creatinine excretion was measured for 3 consecutive days while the subjects received a weight maintenance meat-free diet at the CRC. They also were asked to abstain from meat for 3 days before admission to the CRC. Plasma testosterone concentrations were measured by RIA in the University of Rochester Strong Memorial Hospital clinical laboratories. The interassay coefficient of variation for this assay is 9% at 28 and 43 nmol/L. Paired t tests were used to determine the statistical significance of changes in the variables over time within each group. Unpaired t tests were used for all between-group comparisons. BMR is not directly proportional to LBM, so dividing BMR by LBM is not the correct method to adjust BMR for changes in LBM (6). Instead, we adjusted BMR for LBM using the pooled regression coefficient from an analysis of covariance (8), with LBM as the covariate and BMR as the dependent variable. This coefficient was 2.88 kJ/h f kg LBM, which was very similar to the coefficient obtained using only the baseline data of the subjects in the present study (2.64 kJ/h. kg LBM) and that obtained previously (6) in 47 normal subjects (3.08 kJ/h. kg LBM). Values are expressed as the mean f SEM.
Results Before treatment, there were no significant differences in body weight, LBM, or BMR between control and
testosterone-treated subjects (Table 1). As previously observed (9), the men with muscular dystrophy had lower LBMs (47 + 2 us. 62 f 1 kg) and BMRs (251 f 11 us. 296 + 13 kJ/h) than the normal men (P < 0.02). Body fat (weight minus LBM) tended to be greater in the men with muscular dystrophy (22 + 4 kg) than in the normal men (10 f 2 kg; P < 0.08). Mean plasma testosterone levels increased approxi-
RATE
333
mately 3-fold during testosterone treatment in normal subjects and those with muscular dystrophy, from 20 f 2 to 65 + 8 nmol/L (P < 0.01) after 3 months of treatment. After 12 months, testosterone remained elevated in the treated subjects, at 65 + 14 nmol/L. After 3 months of testosterone treatment, LBM was increased in normal men and those with muscular dystrophy (Table 2). Although the absolute increase in LBM tended to be greater in the normal men, the difference in LBM gains between normal men and those with muscular dystrophy was not significantly different, and the mean percent increase in lean body mass was similar (10% in the men with muscular
dystrophy
and 11% in
the normal subjects). This increase in LBM was paralleled by a slightly smaller increase in body weight (Table 2). After 12 months of testosterone treatment, there was no further increase in LBM or body weight (Table 2). Placebo-treated subjects had no significant change in LBM or body weight after 3 or 12 months (Table 2). After 12 months of treatment in subjects with myotonic dystrophy, the small decrease in fat was different from the increase in body fat in placebo-treated subjects (Table 2). Before testosterone treatment, normal subjects had a higher rate of urinary creatinine excretion (1.80 + 0.17 g/day) than subjects with muscular dystrophy (1.15 + 0.08 g/day; P < 0.01). After 3 months of testosterone treatment, mean urinary creatinine excretion increased 14% (+0.19 + 0.06 g/day; P < O.Ol), with normal men (+13%) and men with muscular dystrophy (+15%) showing similar mean responses. After 12 months of testosterone treatment in subjects with myotonic dystrophy, there was a 57% increase in creatinine excretion (+0.60 + 0.05 g/day; P < 0.01). [After only 3 months of testosterone, these four subjects had a significantly (P < 0.02) smaller (24%) increase in creatinine excretion.] Placebotreated subjects had no significant change in creatinine excretion after 3 months (mean change, +2%), but had a 13% increase in mean creatinine excretion (+0.15 f 0.05 g/day; P < 0.05) after 12 months. Testosterone-treated subjects exhibited a 10% increase in mean BMR after 3 months (Table 3). Eight of the nine subjects with muscular dystrophy and three of four normal subjects had an increased BMR after 3 months of testosterone treatment. The increase in BMR tended to be greater in those with muscular dystrophy than in the normal men, but the difference was not statistically significant
(P > 0.25). The four men with myotonic
dystrophy who were studied after 12 months of testosterone treatment all continued to have an elevated BMR (Table 3). There was no significant change in BMR after 3 or 12 months in subjects who did not receive testosterone (Table 3). When the changes in BMR were adjusted for the
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334
WELLE
JCE& M -1992
ET AL.
Voll4.No2
TABLE 2. Changes in body composition wt
Group
3 months
Testosterone MD Normal Control MD Normal
+3.3 +5.5
+ 1.0”
+
LBM 12 months +2.a
3 months
zk2.7
+4.9 +
1.3”
+1.2 f 1.2 +1.3 * 0.9
+2.4
+
1.3
0.6”.
+6.8
+ 1.9”
-0.6 -0.3
+ 0.9 + 2.4
Fat 12 months
b
3 months
+5.0
f
0.7”vb
-1.6
-1.4
f
1.4
+1.8 +1.7
12 months
f 1.1 -1.3 f 0.8
-2.3
+
+ 1.0
+3.8
+ 1.0”
f
2.5b
1.7
Values are expressed as kilograms (mean + SEM). MD, Muscular dystrophy. a P C 0.05 compared to zero change. b P < 0.05 compared to control group. TABLE 3. Changes in BMR Group Testosterone MD Normal Control MD Normal
Actual change 3 months +32 +20
12 months
+ 7 (9)b +21 f 5 (4)’ f 10 (4)
-21 f 13 (5) +6 f 10 (3)
-6
+ 12 (5)
Adjusted change” 3 months
12 months
+18 + 7 (9)d +3 + 7 (4)
+7 + 7 (4)
-19 f 13 (5) +7 + 8 (3)
-2 + 8 (5)
Values are expressed as kilojoules per h (mean f SEM). The number of subjects is in parentheses. MD, Muscular dystrophy. ’ Adjusted for change in LBM [actual change - (2.88 times kg change in LBM)] . bP < 0.01 compared to zero change and compared to MD control. ‘P < 0.05 compared to zero change; P < 0.10 compared to MD control. d P < 0.05 compared to zero change and compared to MD control.
changes in LBM, there was no significant change in BMR after 3 months of testosterone treatment in normal subjects or after 12 months of testosterone treatment in subjects with muscular dystrophy compared to baseline values and to adjusted changes in BMR in the control groups (Table 3). However, eight of nine men with muscular dystrophy had an increase in adjusted BMR after 3 months of testosterone treatment, which was significantly different from baseline and significantly different from the adjusted change in BMR in the placebo-treated subjects (Table 3). The four subjects who were treated with testosterone for 12 months had an adjusted increase in BMR of 20 +- 6 kJ/h after only 3 months of treatment, which was significantly greater (P < 0.05) than their adjusted change in BMR at 12 months (7 + 7 kJ/h). Discussion Early studies that demonstrated a hypermetabolic effect of testosterone in hypogonadal men (l-3) never clarified whether this effect was secondary to altered body composition or was a direct effect of testosterone on metabolic processes. In the present study of men with muscular dystrophy who had normal testosterone levels before treatment, pharmacological doses of testosterone
increased BMR an average of 13% after 3 months and 9% after 12 months. The normal subjects showed qualitatively the same response, but their increase in BMR was not statistically significant because one subject failed to have an increased BMR after testosterone treatment. With the small number of normal men studied, we do not have adequate statistical power to determine whether normal men and those with muscular dystrophy have quantitatively different responses to testosterone. When the increase in BMR was adjusted for the increase in LBM, a smaller (7%) hypermetabolic effect was observed at 3 months in men with muscular dystrophy. Normal subjects had only a 1% increase in BMR after 3 months of treatment when values were adjusted for the increased LBM, and men with muscular dystrophy had only a 3% increase in adjusted BMR after 12 months (neither change was statistically significant). We conclude that the increase in BMR associated with pharmacological testosterone treatment is primarily mediated by the increase in active cell mass. The anabolic effect of testosterone on muscle is well known (10-12). Hence, the increase in LBM and urinary creatinine excretion was an expected effect of testosterone administration. Assuming that 20 kg muscle produces 1 g/day creatinine in subjects on a meat-free diet (13) muscle mass increased 3.8 kg after 3 months of testosterone treatment, which accounted for 69% of the increase in total LBM. It also appears that reduced muscle mass accounted for nearly all of the difference in total LBM between men with muscular dystrophy and normal men (13.4 of 15 kg). An unexpected finding was that all four of the subjects with myotonic dystrophy who received testosterone for 12 months had an apparent increase in muscle mass that was approximately twice as large as the increase in total LBM. (At 3 months, muscle accounted for an average of 93% of the increase in LBM in these subjects.) One possible explanation for this finding is that prolonged testosterone treatment caused continued growth of skeletal muscle, with a concomitant decline in the mass of some other organs. Another possibility is that prolonged testosterone treatment reduced
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TESTOSTERONE
AND METABOLIC
the potassium content of muscle or some other tissues, causing an underestimation of the increase in LBM. Finally, it is possible that testosterone altered the creatinine output of muscle, so that the increase in muscle mass was overestimated. The metabolic rate per kg resting skeletal muscle is substantially lower than the metabolic rate per kg visceral or neural tissue (14). Hence, if most or all of the increase in LBM is caused by an increase in muscle mass, then we must consider the appropriateness of correcting BMR for total LBM. From forearm oxygen consumption (15, 16) we can estimate the resting energy expenditure of skeletal muscle. Assuming that muscle comprises 72% of the total forearm volume in normal men (17), that forearm tissues other than muscle (bone, fat, and skin) have a negligible metabolic rate, and that forearm muscle is representative of all skeletal muscle, it appears that 1 kg resting muscle expends approximately 2.3 kJ/h. In the present study, the regression coefficient used to adjust changes in BMR was 2.88 kJ/h.kg LBM. This similarity between the theoretical energy utilization of muscle and the value used to adjust BMR for LBM indicates that our adjustment for total LBM was appropriate, even though muscle accounted for most or all of the increase in LBM. Although adult muscular dystrophy patients usually are within normal weight ranges, they tend to be fatter than weight-matched normal subjects. This increased adiposity could have several adverse effects on their general health, as it does in subjects without neuromuscular disease. Thus, an increase in BMR in these subjects is potentially beneficial if it leads to a decrease in body fat. In the present study men with myotonic dystrophy who were treated with placebo gained fat over a 12month period, whereas those treated with testosterone tended to lose fat over the same period. If we assume that the testosterone-treated subjects would have gained as much fat as the placebo-treated subjects in the absence of testosterone, the reduction in body fat over 12 months was approximately 6 kg. The energy equivalent of this amount of fat is 234 MJ or 27 kJ/h over 1 yr, a value similar to the observed increase in BMR.
RATE
335
Acknowledgments We thank Barbara Herr and Brian Hawthorne for their assistance with the data analysis, and Cheryl Porta for performing the 40K analyses.
References 1. McCullagh EP, Rossmiller HR. Methyl testosterone. II. Calorigenic activity. J Clin Endocrinol Metab. 1941;1:503-6. 2. Jones R, McCullagh EP, McCullagh DR, Buckaloo GW. Methyl testosterone. IV. Observations on the hypermetabolism induced by methyl testosterone. J Clin Endocrinol Metab. 1941;1:656-63. 3. Sandiford I, Knowlton K, Kenyon AT. Basal heat production in hypogonadism in men and its increase by protracted treatment with testosterone propionate. J Clin Endocrinol Metab. 1941;1:931-9. 4. Kenyon AT, Knowlton K, Sandiford I, Koch FC, Lotwin G. Comparative study of the metabolic effects of testosterone propionate in normal men and women and in eunuchoidism. Endocrinology. 1940;26:26-45. 5. Kenyon AT, Knowlton K, Lotwin G, Sandiford I. Metabolic response of aged men to testosterone propionate. J Clin Endocrinol Metab. 1942;2:690-5. 6. Welle S, Nair KS. Relationship of resting metabolic rate to body composition and protein turnover. Am J Physiol. 1990;258:E9908. 7. Forbes GB, Schultz F, Cafarelli C, Amirhakimi GH. Effects of body size on potassium-40 measurement in the whole body counter (tiltchair techniauel. Health Phvsics. 1968:15:435-42. 8. Dixon WJ, ed. BMDP statistical software. Berkeley: University of California Press; 1983. 9. Jozefowicz RF, Welle SL, Nair KS, Kingston WJ, Griggs RC. Basal metabolic rate in myotonic dystrophy: evidence against hypometabolism. Neurology. 1987;37:1021-5. 10. Forbes GB. Human body composition. New York: Springer-Verlag; 1987;267-74. 11. Griggs RC, Kingston W, Jozefowicz RF, Herr BE, Forbes G, Halliday G. Effect of testosterone on muscle mass and muscle protein synthesis. J Appl Physiol. 1989;66:498-503. 12. Griggs RC, Pandya S, Florence JM, et al. Randomized controlled trial of testosterone in myotonic dystrophy. Neurology. 1989;39:219-22. 13. Heymsfield SB, Arteaga G, McManus C, Smith J, Moffitt S. Measurement of muscle mass in humans: validity of the 24-hour urinary creatinine method. Am J Clin Nutr. 1983;37:478-94. 14. Brobeck JR, ed. Best and Taylor’s physiological basis of medical practice, 10th ed. Baltimore: Williams and Wilkins; 1979;3/125-6. 15. Jackson RA, Hamling JB, Sim BM, Hawa MI, Blix PM, Nabarro JDN. Peripheral lactate and oxygen metabolism in man: the influence of oral glucose loading. Metabolism. 1987;36:144-50. 16. Elia M, Folmer P, Schlatmann A, Goren A, Austin S. Carbohydrate, fat, and protein metabolism in muscle and in the whole body after mixed meal ingestion. Metabolism. 1988,37:542-51. 17. Maughan RJ, Watson JS, Weir J. The relative proportions of fat, muscle and bone in the normal human forearm as determined by computed tomography. Clin Sci. 198+66:683-g.
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Vol. 74, No. 2 Printed
in U.S.A.
Effect of Testosterone on Metabolic Rate and Body Composition in Normal Men and Men with Muscular Dystrophy* STEPHEN WELLE, RALPH AND ROBERT C. GRIGGS
JOZEFOWICZ,
GILBERT
FORBES,
Departments of Medicine, Neurology, and Pediatrics, Monroe Community Rochester School of Medicine and Dentistry, Rochester, New York 14620
ABSTRACT. We have examined the effect of testosterone enanthate injections (3 mg/kg. week, im) on the basal metabolic rate (BMR) estimated by indirect calorimetry and on lean body mass (LBM) estimated by “‘K counting in four normal men and nine men with muscular dystrophy. Testosterone treatment increased plasma testosterone levels in all subjects (3-fold mean elevation). BMR increased significantly after 3 months of testosterone treatment (mean, 10%; P < 0.01; 13% mean increase in the men with muscular dystrophy and 7% mean increase in the normal subjects). BMR remained elevated (mean increase, 9%) after 12 months of testosterone treatment in four men with muscular dystrophy. LBM also was significantly higher after 3 months of treatment (mean, 10%; P < 0.01) and remained elevated at 12 months. The percent increase in LBM was similar in men with muscular dystrophy (+lO%) and normal men
E
and the University
of
(+ll%). When BMR was adjusted for the increase in LBM by linear regression, the men with muscular dystrophy had an increase in adjusted BMR after 3 months of testosterone treatment (mean increase, 7%), but not after 12 months. The normal men did not have an increase in adjusted BMR. Testosterone treatment for 12 months slightly reduced body fat, whereas there was an increase in body fat in subjects with muscular dystrophy who were treated with placebo for 12 months. We conclude that there is a significant increase in BMR associated with pharmacological testosterone treatment, which for the most part is explained by the increase in LBM. However, in men with muscular dystrophy, there is a small hypermetabolic effect of testosterone beyond that explained by increased LBM. (J Clin Endocrinol Metub 74: 332-335, 1992)
studies of testosterone treatment demonstrated a 5-60% increase in BMR in hypogonadal
ARLY
Because BMR is the largest component of total energy expenditure, an increase in BMR could conceivably produce negative energy balance and reduce body fat.
men (l-3), but did not investigate the mechanism of this effect. Short term (7- to lo-day) administration of testosterone to eugonadal subjects did not increase the basal metabolic rate (BMR) (4,5). No systematic study of the effect of testosterone on metabolic rate in humans has been reported since these early findings. Thus, we have examined the effect of testosterone on BMR in subjects receiving pharmacological doses of testosterone for 3 months or longer. These studies addressed the hypothesis that an increase in BMR induced by testosterone could be explained by increased active cell mass, rather than a direct effect on energy metabolism. We were particularly interested in the effect of testosterone on BMR in sub-
jects with myotonic dystrophy,
Hospital,
Subjects
and Methods
Thirteen men, 18-45 yr old, were studied before and after a S-month period of testosterone administration. Nine of the subjects (seven with myotonic dystrophy, one with limb girdle dystrophy, and one with facioscapulohumeral dystrophy) were participating in therapeutic trials of testosterone. Four of the subjects were normal volunteers. Four of the subjects with myotonic dystrophy were also studied after 12 months of testosterone treatment. We also studied a control group comprised of five men with myotonic dystrophy treated with placebo for 12 months and three normal men whose BMR and lean body mass (LBM) measurements were repeated after a 3-month interval with no interventions. Mean ages, weights, baseline BMRs, and LBMs of each group are given in Table 1. Written and verbal informed consent was obtained from all subjects after the protocol was approved by the University of Rochester Research Subjects Review Board. BMR, LBM, 24-h urinary creatinine excretion (an index of muscle mass), and plasma levels of testosterone were measured before and after 3 months of treatment in all subjects, except
who have a high body fat
content even though total body weight is usually normal. Received April 10, 1991. Address all correspondence and requests for reprints to: Stephen Welle, Monroe Community Hospital, 435 East Henrietta Road, Endocrine Unit, Room 3C-22, Rochester, New York 14620. * This work was supported by grants from the NIH (N&22099, DK39063, HD-18454, and RR-00044) and the Muscular Dystrophy Association. 332
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TESTOSTERONE
AND METABOLIC
TABLE 1. Baseline weight, LBM, fat, and BMR Age W Testosterone-treated subjects Normal (n = 4) Muscular dystrophy (n = 9) Control subjects Normal (n = 3) Muscular dystrophy (n = 5)
Wt (kg)
LBM (kg)
Fat 04
BMR
&J/h)
33*3 73+5 62+2 llf4 304+23 32 f 3 69 + 5 47 + 3 22 + 5 251 + 13 22 + 1 72 + 1 62 f2 lo+ 2 286+ 5 34 + 4 70 f 5 47 + 5 23 + 8 249 + 20
Values are the mean + SEM.
that the three untreated normal volunteers had measurements of only BMR and LBM. The same variables were measured after 12 months in the placebo- and testosterone-treated subjects who participated in the longer protocol. Testosterone was administered weekly by a nurse as testosterone enanthate (3 mg/kg, im). BMR was measured after an overnight fast in the Clinical Research Center (CRC), using a ventilated mask indirect calorimetry method with a coefficient of variation (within days and between days) of less than 5% (6). LBM was determined by 40K counting, which has a coefficient of variation of 3% (7). Urinary creatinine excretion was measured for 3 consecutive days while the subjects received a weight maintenance meat-free diet at the CRC. They also were asked to abstain from meat for 3 days before admission to the CRC. Plasma testosterone concentrations were measured by RIA in the University of Rochester Strong Memorial Hospital clinical laboratories. The interassay coefficient of variation for this assay is 9% at 28 and 43 nmol/L. Paired t tests were used to determine the statistical significance of changes in the variables over time within each group. Unpaired t tests were used for all between-group comparisons. BMR is not directly proportional to LBM, so dividing BMR by LBM is not the correct method to adjust BMR for changes in LBM (6). Instead, we adjusted BMR for LBM using the pooled regression coefficient from an analysis of covariance (8), with LBM as the covariate and BMR as the dependent variable. This coefficient was 2.88 kJ/h f kg LBM, which was very similar to the coefficient obtained using only the baseline data of the subjects in the present study (2.64 kJ/h. kg LBM) and that obtained previously (6) in 47 normal subjects (3.08 kJ/h. kg LBM). Values are expressed as the mean f SEM.
Results Before treatment, there were no significant differences in body weight, LBM, or BMR between control and
testosterone-treated subjects (Table 1). As previously observed (9), the men with muscular dystrophy had lower LBMs (47 + 2 us. 62 f 1 kg) and BMRs (251 f 11 us. 296 + 13 kJ/h) than the normal men (P < 0.02). Body fat (weight minus LBM) tended to be greater in the men with muscular dystrophy (22 + 4 kg) than in the normal men (10 f 2 kg; P < 0.08). Mean plasma testosterone levels increased approxi-
RATE
333
mately 3-fold during testosterone treatment in normal subjects and those with muscular dystrophy, from 20 f 2 to 65 + 8 nmol/L (P < 0.01) after 3 months of treatment. After 12 months, testosterone remained elevated in the treated subjects, at 65 + 14 nmol/L. After 3 months of testosterone treatment, LBM was increased in normal men and those with muscular dystrophy (Table 2). Although the absolute increase in LBM tended to be greater in the normal men, the difference in LBM gains between normal men and those with muscular dystrophy was not significantly different, and the mean percent increase in lean body mass was similar (10% in the men with muscular
dystrophy
and 11% in
the normal subjects). This increase in LBM was paralleled by a slightly smaller increase in body weight (Table 2). After 12 months of testosterone treatment, there was no further increase in LBM or body weight (Table 2). Placebo-treated subjects had no significant change in LBM or body weight after 3 or 12 months (Table 2). After 12 months of treatment in subjects with myotonic dystrophy, the small decrease in fat was different from the increase in body fat in placebo-treated subjects (Table 2). Before testosterone treatment, normal subjects had a higher rate of urinary creatinine excretion (1.80 + 0.17 g/day) than subjects with muscular dystrophy (1.15 + 0.08 g/day; P < 0.01). After 3 months of testosterone treatment, mean urinary creatinine excretion increased 14% (+0.19 + 0.06 g/day; P < O.Ol), with normal men (+13%) and men with muscular dystrophy (+15%) showing similar mean responses. After 12 months of testosterone treatment in subjects with myotonic dystrophy, there was a 57% increase in creatinine excretion (+0.60 + 0.05 g/day; P < 0.01). [After only 3 months of testosterone, these four subjects had a significantly (P < 0.02) smaller (24%) increase in creatinine excretion.] Placebotreated subjects had no significant change in creatinine excretion after 3 months (mean change, +2%), but had a 13% increase in mean creatinine excretion (+0.15 f 0.05 g/day; P < 0.05) after 12 months. Testosterone-treated subjects exhibited a 10% increase in mean BMR after 3 months (Table 3). Eight of the nine subjects with muscular dystrophy and three of four normal subjects had an increased BMR after 3 months of testosterone treatment. The increase in BMR tended to be greater in those with muscular dystrophy than in the normal men, but the difference was not statistically significant
(P > 0.25). The four men with myotonic
dystrophy who were studied after 12 months of testosterone treatment all continued to have an elevated BMR (Table 3). There was no significant change in BMR after 3 or 12 months in subjects who did not receive testosterone (Table 3). When the changes in BMR were adjusted for the
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334
WELLE
JCE& M -1992
ET AL.
Voll4.No2
TABLE 2. Changes in body composition wt
Group
3 months
Testosterone MD Normal Control MD Normal
+3.3 +5.5
+ 1.0”
+
LBM 12 months +2.a
3 months
zk2.7
+4.9 +
1.3”
+1.2 f 1.2 +1.3 * 0.9
+2.4
+
1.3
0.6”.
+6.8
+ 1.9”
-0.6 -0.3
+ 0.9 + 2.4
Fat 12 months
b
3 months
+5.0
f
0.7”vb
-1.6
-1.4
f
1.4
+1.8 +1.7
12 months
f 1.1 -1.3 f 0.8
-2.3
+
+ 1.0
+3.8
+ 1.0”
f
2.5b
1.7
Values are expressed as kilograms (mean + SEM). MD, Muscular dystrophy. a P C 0.05 compared to zero change. b P < 0.05 compared to control group. TABLE 3. Changes in BMR Group Testosterone MD Normal Control MD Normal
Actual change 3 months +32 +20
12 months
+ 7 (9)b +21 f 5 (4)’ f 10 (4)
-21 f 13 (5) +6 f 10 (3)
-6
+ 12 (5)
Adjusted change” 3 months
12 months
+18 + 7 (9)d +3 + 7 (4)
+7 + 7 (4)
-19 f 13 (5) +7 + 8 (3)
-2 + 8 (5)
Values are expressed as kilojoules per h (mean f SEM). The number of subjects is in parentheses. MD, Muscular dystrophy. ’ Adjusted for change in LBM [actual change - (2.88 times kg change in LBM)] . bP < 0.01 compared to zero change and compared to MD control. ‘P < 0.05 compared to zero change; P < 0.10 compared to MD control. d P < 0.05 compared to zero change and compared to MD control.
changes in LBM, there was no significant change in BMR after 3 months of testosterone treatment in normal subjects or after 12 months of testosterone treatment in subjects with muscular dystrophy compared to baseline values and to adjusted changes in BMR in the control groups (Table 3). However, eight of nine men with muscular dystrophy had an increase in adjusted BMR after 3 months of testosterone treatment, which was significantly different from baseline and significantly different from the adjusted change in BMR in the placebo-treated subjects (Table 3). The four subjects who were treated with testosterone for 12 months had an adjusted increase in BMR of 20 +- 6 kJ/h after only 3 months of treatment, which was significantly greater (P < 0.05) than their adjusted change in BMR at 12 months (7 + 7 kJ/h). Discussion Early studies that demonstrated a hypermetabolic effect of testosterone in hypogonadal men (l-3) never clarified whether this effect was secondary to altered body composition or was a direct effect of testosterone on metabolic processes. In the present study of men with muscular dystrophy who had normal testosterone levels before treatment, pharmacological doses of testosterone
increased BMR an average of 13% after 3 months and 9% after 12 months. The normal subjects showed qualitatively the same response, but their increase in BMR was not statistically significant because one subject failed to have an increased BMR after testosterone treatment. With the small number of normal men studied, we do not have adequate statistical power to determine whether normal men and those with muscular dystrophy have quantitatively different responses to testosterone. When the increase in BMR was adjusted for the increase in LBM, a smaller (7%) hypermetabolic effect was observed at 3 months in men with muscular dystrophy. Normal subjects had only a 1% increase in BMR after 3 months of treatment when values were adjusted for the increased LBM, and men with muscular dystrophy had only a 3% increase in adjusted BMR after 12 months (neither change was statistically significant). We conclude that the increase in BMR associated with pharmacological testosterone treatment is primarily mediated by the increase in active cell mass. The anabolic effect of testosterone on muscle is well known (10-12). Hence, the increase in LBM and urinary creatinine excretion was an expected effect of testosterone administration. Assuming that 20 kg muscle produces 1 g/day creatinine in subjects on a meat-free diet (13) muscle mass increased 3.8 kg after 3 months of testosterone treatment, which accounted for 69% of the increase in total LBM. It also appears that reduced muscle mass accounted for nearly all of the difference in total LBM between men with muscular dystrophy and normal men (13.4 of 15 kg). An unexpected finding was that all four of the subjects with myotonic dystrophy who received testosterone for 12 months had an apparent increase in muscle mass that was approximately twice as large as the increase in total LBM. (At 3 months, muscle accounted for an average of 93% of the increase in LBM in these subjects.) One possible explanation for this finding is that prolonged testosterone treatment caused continued growth of skeletal muscle, with a concomitant decline in the mass of some other organs. Another possibility is that prolonged testosterone treatment reduced
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TESTOSTERONE
AND METABOLIC
the potassium content of muscle or some other tissues, causing an underestimation of the increase in LBM. Finally, it is possible that testosterone altered the creatinine output of muscle, so that the increase in muscle mass was overestimated. The metabolic rate per kg resting skeletal muscle is substantially lower than the metabolic rate per kg visceral or neural tissue (14). Hence, if most or all of the increase in LBM is caused by an increase in muscle mass, then we must consider the appropriateness of correcting BMR for total LBM. From forearm oxygen consumption (15, 16) we can estimate the resting energy expenditure of skeletal muscle. Assuming that muscle comprises 72% of the total forearm volume in normal men (17), that forearm tissues other than muscle (bone, fat, and skin) have a negligible metabolic rate, and that forearm muscle is representative of all skeletal muscle, it appears that 1 kg resting muscle expends approximately 2.3 kJ/h. In the present study, the regression coefficient used to adjust changes in BMR was 2.88 kJ/h.kg LBM. This similarity between the theoretical energy utilization of muscle and the value used to adjust BMR for LBM indicates that our adjustment for total LBM was appropriate, even though muscle accounted for most or all of the increase in LBM. Although adult muscular dystrophy patients usually are within normal weight ranges, they tend to be fatter than weight-matched normal subjects. This increased adiposity could have several adverse effects on their general health, as it does in subjects without neuromuscular disease. Thus, an increase in BMR in these subjects is potentially beneficial if it leads to a decrease in body fat. In the present study men with myotonic dystrophy who were treated with placebo gained fat over a 12month period, whereas those treated with testosterone tended to lose fat over the same period. If we assume that the testosterone-treated subjects would have gained as much fat as the placebo-treated subjects in the absence of testosterone, the reduction in body fat over 12 months was approximately 6 kg. The energy equivalent of this amount of fat is 234 MJ or 27 kJ/h over 1 yr, a value similar to the observed increase in BMR.
RATE
335
Acknowledgments We thank Barbara Herr and Brian Hawthorne for their assistance with the data analysis, and Cheryl Porta for performing the 40K analyses.
References 1. McCullagh EP, Rossmiller HR. Methyl testosterone. II. Calorigenic activity. J Clin Endocrinol Metab. 1941;1:503-6. 2. Jones R, McCullagh EP, McCullagh DR, Buckaloo GW. Methyl testosterone. IV. Observations on the hypermetabolism induced by methyl testosterone. J Clin Endocrinol Metab. 1941;1:656-63. 3. Sandiford I, Knowlton K, Kenyon AT. Basal heat production in hypogonadism in men and its increase by protracted treatment with testosterone propionate. J Clin Endocrinol Metab. 1941;1:931-9. 4. Kenyon AT, Knowlton K, Sandiford I, Koch FC, Lotwin G. Comparative study of the metabolic effects of testosterone propionate in normal men and women and in eunuchoidism. Endocrinology. 1940;26:26-45. 5. Kenyon AT, Knowlton K, Lotwin G, Sandiford I. Metabolic response of aged men to testosterone propionate. J Clin Endocrinol Metab. 1942;2:690-5. 6. Welle S, Nair KS. Relationship of resting metabolic rate to body composition and protein turnover. Am J Physiol. 1990;258:E9908. 7. Forbes GB, Schultz F, Cafarelli C, Amirhakimi GH. Effects of body size on potassium-40 measurement in the whole body counter (tiltchair techniauel. Health Phvsics. 1968:15:435-42. 8. Dixon WJ, ed. BMDP statistical software. Berkeley: University of California Press; 1983. 9. Jozefowicz RF, Welle SL, Nair KS, Kingston WJ, Griggs RC. Basal metabolic rate in myotonic dystrophy: evidence against hypometabolism. Neurology. 1987;37:1021-5. 10. Forbes GB. Human body composition. New York: Springer-Verlag; 1987;267-74. 11. Griggs RC, Kingston W, Jozefowicz RF, Herr BE, Forbes G, Halliday G. Effect of testosterone on muscle mass and muscle protein synthesis. J Appl Physiol. 1989;66:498-503. 12. Griggs RC, Pandya S, Florence JM, et al. Randomized controlled trial of testosterone in myotonic dystrophy. Neurology. 1989;39:219-22. 13. Heymsfield SB, Arteaga G, McManus C, Smith J, Moffitt S. Measurement of muscle mass in humans: validity of the 24-hour urinary creatinine method. Am J Clin Nutr. 1983;37:478-94. 14. Brobeck JR, ed. Best and Taylor’s physiological basis of medical practice, 10th ed. Baltimore: Williams and Wilkins; 1979;3/125-6. 15. Jackson RA, Hamling JB, Sim BM, Hawa MI, Blix PM, Nabarro JDN. Peripheral lactate and oxygen metabolism in man: the influence of oral glucose loading. Metabolism. 1987;36:144-50. 16. Elia M, Folmer P, Schlatmann A, Goren A, Austin S. Carbohydrate, fat, and protein metabolism in muscle and in the whole body after mixed meal ingestion. Metabolism. 1988,37:542-51. 17. Maughan RJ, Watson JS, Weir J. The relative proportions of fat, muscle and bone in the normal human forearm as determined by computed tomography. Clin Sci. 198+66:683-g.
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