Total-body skeletal muscle mass: evaluation of 24-h urinary creatinine excretion by computerized axial tomography

An estimate of total body muscle mass with dual-energy X-ray absorptiometry (DXA; appendicular muscle mass divided by 0.75) was compared with 24-h urinary creatinine excretion in 59 healthy men and women [20–30 yr (younger), 45–59 yr (middle age), and 60–79 yr (older)] who stayed in a clinical research center for 5 days. Total body water (2H2O dilution), fat (underwater weighing), bone mineral (DXA), and total body protein mass (based on a 4-compartment model) were also measured. Muscle mass estimates by DXA and creatinine were highly correlated ( r = 0.80). However, stepwise multiple regression indicated that a significant amount of additional between-subject variability in DXA-based muscle mass estimates could be explained by total body water. Creatinine excretion, knee extensor strength, and total body protein mass all decreased with age, suggesting a decline in muscle cell mass with aging. However, DXA-based muscle mass and measures of nonfat body mass (i.e., lean body mass by2H2O and fat-free body mass by underwater weighing) did not change with age. These results indicate that DXA and urinary creatinine excretion give different results regarding the decline in total body muscle mass with aging. The factor(s) responsible for the apparent underestimate of age-related sarcopenia by DXA remain to be fully defined, but changes in body water may be an important contributor.

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Total plasma creatinine: an accurate measure of total striated muscle mass

Journal of Applied Physiology ◽

10.1152/jappl.1981.51.3.762 ◽

1981 ◽

Vol 51 (3) ◽

pp. 762-766 ◽

Cited By ~ 57

Author(s):

J. E. Schutte ◽

J. C. Longhurst ◽

F. A. Gaffney ◽

B. C. Bastian ◽

C. G. Blomqvist

Keyword(s):

Body Composition ◽

Muscle Mass ◽

Total Body Water ◽

Striated Muscle ◽

Plasma Creatinine ◽

Total Plasma ◽

Creatinine Excretion ◽

Urinary Creatinine ◽

Total Body ◽

Urinary Creatinine Excretion

Creatinine is a metabolite unique to striated muscle. Measurement of 24-h urinary creatinine excretion is an established method for estimating striated muscle mass. However, accurate assessment of urinary creatinine excretion is often impractical. We investigated the hypothesis that total plasma creatinine could be used instead of urinary creatinine excretion to estimate body composition. In 24 men, plasma volume and plasma creatinine concentration were measured, and total plasma creatinine was calculated as the product of these two measurements. Other measurements included urinary creatinine excretion, total body water, and anthropometry. Total plasma creatinine correlated strongly with urinary creatinine excretion (r = 0.82) and with weight, total body water, and anthropometrically estimated lean body mass. Muscle mass could be predicted by the equation: 0.88 x total plasma creatinine (mg). To verify this relationship, total plasma creatinine was prospectively measured in four dogs, then their total striated muscle was removed and weighed. Predicted muscle mass was within +/- 3.9% (range = 0.5–10.8%) of observed muscle mass. The ability to estimate muscle mass conveniently and accurately from total plasma creatinine should prove valuable for future studies in physiology and body composition.

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Creatinine Excretion

PEDIATRICS ◽

10.1542/peds.71.1.140a ◽

1983 ◽

Vol 71 (1) ◽

pp. 140-140

Author(s):

JAMES L. SUTPHEN

Keyword(s):

Muscle Mass ◽

Initial Presentation ◽

Creatinine Excretion ◽

Urinary Creatinine ◽

Weight Measurement ◽

Body Muscle ◽

Creatinine Measurement ◽

Urinary Creatinine Excretion

In Reply.— The questions posed by Harkavy allow me to expand on the initial presentation of the data in my previous report.1 As documented by numerous previous reports, urinary creatinine excretion does, in fact, reflect body muscle mass.2 Furthermore, it has been documented in older infants that creatinine excretion per kilogram increases with the age, weight, and length of the infant.3 The regression data in my report are not expressed in terms of creatinine per kilogram as the dependent variable as this multiplies the error of creatinine measurement by including the error in weight measurement (hydration states etc).

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