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      Predictors of skeletal muscle mass in elderly men and women.

      Mechanisms of Ageing and Development

      Aged, Aged, 80 and over, Aging, metabolism, physiology, Body Composition, Female, Humans, Male, Muscle, Skeletal

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          Abstract

          Elderly men and women lose muscle mass and strength with increasing age. Decreased physical activity, hormones, malnutrition and chronic disease have been identified as factors contributing to this loss. There are few data, however, for their multivariate associations with muscle mass and strength. This study analyzes these associations in a cross-sectional sample of elderly people from the New Mexico Aging Process Study. Data collected in 1994 for 121 male and 180 female volunteers aged 65-97 years of age enrolled in The New Mexico Aging Process Study were analyzed. Body composition was measured using dual energy X-ray absorptiometry; dietary intake from 3 day food records; usual physical activity by questionnaire; health status from annual physical examinations; and serum testosterone, estrone, sex-hormone binding globulin (SHBG), and insulin-like growth factor (IGF1) from radioimmunoassays of fasting blood samples. Statistical analyses included partial correlation and stepwise multiple regression. The muscle mass and strength (adjusted for knee height) decreased with increasing age in both sexes. The muscle mass was significantly associated with serum free-testosterone, physical activity, cardiovascular disease, and IGF1 in the men. In the women, the muscle mass was significantly associated with total fat mass and physical activity. Age was not associated significantly with muscle mass after controlling for these variables. Grip strength was associated with age independent of muscle mass in both sexes. Estrogen (endogenous and exogenous) was not associated with muscle mass or strength in women. Age-related loss of muscle mass and strength occurs in relatively healthy, well-nourished elderly men and women and has a multifactorial basis. Sex hormone status is an important factor in men but not in women. Physical activity is an important predictor of muscle mass in both sexes.

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          Most cited references 10

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          The effects of treatment with recombinant human growth hormone on body composition and metabolism in adults with growth hormone deficiency.

          In a double-blind, placebo-controlled trial, we studied the effects of six months of growth hormone replacement in 24 adults with growth hormone deficiency. Most of the patients had acquired growth hormone deficiency during adulthood as a consequence of treatment for pituitary tumors, and all were receiving appropriate thyroid, adrenal, and gonadal hormone replacement. The daily dose of recombinant human growth hormone (rhGH) was 0.07 U per kilogram of body weight, given subcutaneously at bedtime. The mean (+/- SE) plasma concentration of insulin-like growth factor I increased from 0.41 +/- 0.05 to 1.53 +/- 0.16 U per liter during rhGH treatment. Treatment with rhGH had no effect on body weight. The mean lean body mass, however, increased by 5.5 +/- 1.1 kg (P less than 0.0001), and the fat mass decreased by 5.7 +/- 0.9 kg (P less than 0.0001) in the group treated with growth hormone; neither changed significantly in the placebo group. The basal metabolic rate, measured at base line and after one and six months of rhGH administration, increased significantly; the respective values were 32.4 +/- 1.4, 37.2 +/- 2.2, and 34.4 +/- 1.6 kcal per kilogram of lean body mass per day (P less than 0.001 for both comparisons). Fasting plasma cholesterol levels were lower (P less than 0.05) in the rhGH-treated group than in the placebo group, whereas plasma triglyceride values were similar in the two groups throughout the study. We conclude that growth hormone has a role in the regulation of body composition in adults, probably through its anabolic and lipolytic actions.
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            Longitudinal changes in testosterone, luteinizing hormone, and follicle-stimulating hormone in healthy older men.

            Cross-sectional studies have demonstrated a decline in testosterone and free and bioavailable testosterone with age. This occurs in a majority of older persons without an increase in luteinizing hormone (LH), suggesting that a component of the testosterone decrease is due to secondary hypogonadism. To determine whether these findings could be duplicated in a longitudinal study, we measured testosterone, LH, follicle-stimulating hormone (FSH), and sex hormone-binding globulin (SHBG) levels in 77 men participating in the New Mexico Aging Process Study who had sera available in 1980 or 1981 and two or more serial samples in 1982, 1984, 1989, and/or 1994. Thirty-nine subjects had samples available from both 1980 and 1994. The age at entry into the study ranged from 61 to 87 years. Testosterone levels decreased over the 15 years of the study. In persons who were alive for the duration of the study, testosterone levels were significantly lower 5 years before termination of the study (P < .05). Testosterone levels did not differ at entry into the study among those who died and those who were alive at the end of the study period. Eight of 77 subjects (10%) had LH levels above the normal range at some time during the study. In contrast, 43% of subjects had elevated FSH levels. Both LH and FSH increased significantly with age. SHBG levels were measured in 1980 and 1994 and increased significantly with age (P < .0001). LH and FSH were highly correlated with one another, but neither correlated with testosterone. This study demonstrated a longitudinal decline in testosterone and an increase in LH and FSH in older men. The average rate of decrement in testosterone concentration was 110 ng/dL every decade.
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              Impaired growth hormone secretion in the adult population: relation to age and adiposity.

              Growth hormone (GH) release was studied in adults of normal stature, ages 21-86 yr. The subjects were 85-115% of ideal body weight, between the 5th and 95th percentiles in height, and free of active or progressive disease. 9 to 12 individuals in each decade from thirds to ninth were evaluated. The following criteria of GH status were measured: serum GH concentration, analyzed by radioimmunoassay at half-hour intervals for 4 h after onset of sleep, and at 1-h intervals from 8 a.m. to 4 p.m. in 52 subjects; daily retention of N, P, and K in response to 0.168 U human (h)GH/kg body wt3/4/day in 18 subjects; and plasma somatomedin C (SmC) level before and during exogenous hGH treatment in 18 subjects. All 10 individuals, 20-29 yr old, released substantial amounts of endogenous GH during both day and night (average peak serum GH obtained during day and night was 7.3 and 20.3 ng/ml, respectively); average plasma SmC was 1.43 U/ml (95% tolerance limits, 0.64-2.22 U/ml). There was no significant effect of exogenous hGH on elemental balances or on plasma SmC. In contrast, 6 of 12 individuals 60-79 yr old showed the following evidences of impaired GH release; peak waking and sleeping serum GH less than 4 ng/ml; plasma SmC less than 0.38 U/ml; a significant retention in N, P, and K; and a significant rise in plasma SmC, in response to exogenous hGH. Plasma SmC, serum GH during sleep, serum GH during the day, retentions of N, P, and K in response to exogenous hGH, and rise in plasma SmC in response to hGH were all intercorrelated (P less than 0.05). Plasma SmC less than 0.38 U/ml corresponded to peak nocturnal serum GH less than 4 ng/ml. The prevalence of plasma SmC less than 0.38 U/ml increased progressively from age 20 to 90: third decade, 0%; fourth, 11%; fifth, 20%; sixth, 22%; seventh, 42%; eight, 55%; and ninth, 55%. Within each decade, plasma SmC was inversely related to adiposity.
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                Author and article information

                Journal
                10220041

                Chemistry

                Aged, Aged, 80 and over, Aging, metabolism, physiology, Body Composition, Female, Humans, Male, Muscle, Skeletal

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