Effects of heavy-resistance training on hormonal  response patterns in younger vs. older men

To examine the adaptations of the endocrine system to heavy-resistance training in younger vs. older men, two groups of men (30 and 62 yr old) participated in a 10-wk periodized strength-power training program. Blood was obtained before, immediately after, and 5, 15, and 30 min after exercise at rest before and after training and at rest at −3, 0, 6, and 10 wk for analysis of total testosterone, free testosterone, cortisol, growth hormone, lactate, and ACTH analysis. Resting values for insulin-like growth factor (IGF)-I and IGF-binding protein-3 were determined before and after training. A heavy-resistance exercise test was used to evaluate the exercise-induced responses (4 sets of 10-repetition maximum squats with 90 s of rest between sets). Squat strength and thigh muscle cross-sectional area increased for both groups. The younger group demonstrated higher total and free testosterone and IGF-I than the older men, training-induced increases in free testosterone at rest and with exercise, and increases in resting IGF-binding protein-3. With training the older group demonstrated a significant increase in total testosterone in response to exercise stress along with significant decreases in resting cortisol. These data indicate that older men do respond with an enhanced hormonal profile in the early phase of a resistance training program, but the response is different from that of younger men.

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Relationship of chronic endurance exercise to the somatotropic and sex hormone status of older men

Acta Endocrinologica ◽

10.1530/eje.0.1380517 ◽

1998 ◽

pp. 517-523 ◽

Cited By ~ 26

Author(s):

CS Cooper ◽

DR Taaffe ◽

D Guido ◽

E Packer ◽

L Holloway ◽

...

Keyword(s):

Body Composition ◽

Muscle Strength ◽

Endurance Exercise ◽

Free Testosterone ◽

Older Men ◽

Sex Hormone ◽

Group Differences ◽

Total Testosterone ◽

Free Androgen Index ◽

Igf I

To investigate putative abrogating effects of habitual endurance exercise on age-related changes in endocrine function and body composition, we compared insulin-like growth factor-I (IGF-I), sex hormonal status and body composition in 15 Masters runners and 15 minimally exercising men (MEM) aged 60-70 years. A higher maximal oxygen uptake (VO2 max.) in the runners (41.4+/-1.6 compared with 27.3+/-1.4 ml/kg/min, P=0.0001; mean+/-S.E.M.) reflected our group allocations. Analysis of body composition and bone mineral density (BMD) by dual energy X-ray absorptiometry showed no group differences in lean tissue mass or in regional or whole body BMD, but MEM were heavier, reflecting greater adiposity. Of nine muscle groups tested, only quadriceps strength differed significantly, being greater in runners (60.3+/-2.8 compared with 51.1+/-2.3 kg, P=0.02). Total IGF-I (129+/-10 compared with 124+/-11 ng/ml, P=0.72) and IGF-binding protein-3 (2854+/-94 compared with 2623+/-128ng/ml, P=0.16), were similarly depressed compared with young adult norms in both groups. There was no relationship between total or bioavailable IGF-I and any body composition, BMD or muscle strength variable. In the runners, concentrations of total testosterone (19.1+/-0.8 compared with 15.0+/-0.9 nmol/l, P=0.002) and sex hormone binding globulin (SHBG) (124.4+/-21.6 compared with 67.7+/-11.6 nmol/l, P=0.03) were significantly greater, but the free androgen index was significantly lower (20.7+/-2.7 compared with 31.4+/-4.1, P=0.04). Directly measured free testosterone, however, was similar between the runners and MEM (47.9+/-1.8 compared with 47.1+/-2.0 nmol/l P=0.80). Therefore the group differences in total testosterone and free androgen index were due to their different SHBG concentrations. Although estrone concentration was higher in MEM (85.1+/-5.2 compared with 108+/-6.7 pmol/l, P=0.03), estradiol concentration was similar between groups (73.0+/-6.3 compared with 81.8+/-8.0 pmol/l, P=0.18), indicating that estrogens were not responsible for the increased SHBG in runners. These results indicate that even high levels of regular endurance exercise do not prevent the decline in the somatotropic axis that occurs with aging. Furthermore, the somatic effects of exercise in older men (reduced adiposity and increased regional muscle strength) occurred independently of somatotropic or androgen status. Although habitual exercise does not influence free testosterone concentrations in older men, it appears to enhance the age-associated increase in SHBG synthesis.

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Ontogenic and nutritional changes in circulating insulin-like growth factor (IGF)-I, IGF-II and IGF-binding proteins in growing ewe and ram lambs

Journal of Endocrinology ◽

10.1677/joe.0.1550047 ◽

1997 ◽

Vol 155 (1) ◽

pp. 47-54 ◽

Cited By ~ 13

Author(s):

KL Gatford ◽

KJ Quinn ◽

PE Walton ◽

PA Grant ◽

BJ Hosking ◽

...

Keyword(s):

Sex Differences ◽

Feed Intake ◽

Plasma Concentrations ◽

Endocrine System ◽

Igf Binding Proteins ◽

Igf I ◽

Before And After ◽

Igf Binding ◽

Igf Binding Protein ◽

Igfbp 3

The ontogeny of the IGF endocrine system was investigated in 15 young lambs before and after weaning at 62 days of age. Before weaning, plasma IGF-I concentrations were higher in rams than ewes, and plasma concentrations of IGF-II and IGF-binding protein-3 (IGFBP-3) also tended to be higher in rams than in ewes. Feed intake of ewes and rams was restricted after weaning to remove sex differences in feed intake. Plasma concentrations of IGF-I and IGFBP-3 did not differ between rams and ewes at 100 days of age, but plasma IGF-II was higher in rams than in ewes at this time. Since circulating concentrations of GH were higher in rams than in ewes at 100 days of age, this implies that the restricted feed intake blocked the IGF-I and IGFBP-3 responses to GH. We conclude that sex differences in circulating IGF-I and IGFBP-3 concentrations in the growing lamb alter with age, and are not present when nutrition is restricted.

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Efficacy of myonuclear addition may explain differential myofiber growth among resistance-trained young and older men and women

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00190.2006 ◽

2006 ◽

Vol 291 (5) ◽

pp. E937-E946 ◽

Cited By ~ 217

Author(s):

John K. Petrella ◽

Jeong-su Kim ◽

James M. Cross ◽

David J. Kosek ◽

Marcas M. Bamman

Keyword(s):

Resistance Training ◽

Cell Activation ◽

Vastus Lateralis ◽

Knee Extensor ◽

Free Testosterone ◽

Sex Hormone Binding Globulin ◽

Muscle Stem Cells ◽

Igf I ◽

Paracrine Growth Factors ◽

Igf Binding

Skeletal muscle stem (satellite) cells supporting growth/regeneration are thought to be activated and incorporated into growing myofibers by both endocrine and locally expressed autocrine/paracrine growth factors, the latter being load sensitive. We recently found that myofiber hypertrophy with resistance training is superior in young men (YM) vs. young women and older adults (Kosek DJ, Kim JS, Petrella JK, Cross JM, and Bamman MM. J Appl Physiol 101: 531–544, 2006). We hypothesized that the advanced myofiber hypertrophy in YM is facilitated by myonuclear addition in response to a milieu promoting stem cell activation. Twenty-six young (27.0 ± 1 yr, 50% women) and 26 older (63.7 ± 1 yr, 50% women) adults completed 16 wk of knee extensor resistance training. Vastus lateralis biopsies were obtained at baseline, 24 h after one bout, and after 16 wk. Muscle stem cells were identified immunohistochemically with anti-neural cell adhesion molecule (NCAM+). Muscle transcript levels of IGF-I and mechanogrowth factor (MGF) were determined by RT-PCR. Serum IGF-I, IGF-binding protein (IGFBP)-3, IGFBP-1, total and free testosterone, sex hormone-binding globulin (SHBG), and androstenedione were assessed by radioimmunoassay. Myofiber hypertrophy was twofold greater in YM vs. others, and only YM increased NCAM+ cells per 100 myofibers (49%) and myonuclei per fiber (19%) ( P < 0.05). IGF-IEa mRNA was higher in young and increased acutely (29%) with summation by 16 wk (96%) ( P < 0.05). MGF mRNA increased only in young after one bout (81%) and by 16 wk (85%) ( P < 0.001). Circulating IGF-I was twofold higher in young, whereas IGFBP-1 was lowest in YM ( P < 0.05). Among men, free testosterone was 59% higher in YM ( P < 0.01). Myonuclear addition was most effectively accomplished in YM, which likely drove the superior growth.

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Testosterone and Estradiol Regulate Free Insulin-Like Growth Factor I (IGF-I), IGF Binding Protein 1 (IGFBP-1), and Dimeric IGF-I/IGFBP-1 Concentrations

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2004-1314 ◽

2005 ◽

Vol 90 (5) ◽

pp. 2941-2947 ◽

Cited By ~ 25

Author(s):

Johannes D. Veldhuis ◽

Jan Frystyk ◽

Ali Iranmanesh ◽

Hans Ørskov

Keyword(s):

Healthy Aging ◽

Binding Protein ◽

Older Men ◽

Factor I ◽

Free Insulin ◽

Igf I ◽

Igf Binding ◽

Aging Adults ◽

Igf Binding Protein ◽

Biological Actions

The present study tests the clinical postulate that elevated testosterone (Te) and estradiol (E2) concentrations modulate the effects of constant iv infusion of saline vs. recombinant human IGF-I on free IGF-I, IGF binding protein (IGFBP)-1, and dimeric IGF-I/IGFBP-1 concentrations in healthy aging adults. To this end, comparisons were made after administration of placebo (Pl) vs. Te in eight older men (aged 61 ± 4 yr) and after Pl vs. E2 in eight postmenopausal women (62 ± 3 yr). In the saline session, E2 lowered and Te increased total IGF-I; E2 specifically elevated IGFBP-1 by 1.5-fold and suppressed free IGF-I by 34%; and E2 increased binary IGF-I/IGFBP-1 by 5-fold more than Te. During IGF-I infusion, the following were found: 1) total and free IGF-I rose 1.4- to 2.0-fold (Pl) and 2.1–2.5-fold (Te) more rapidly in men than women; 2) binary IGF-I/IGFBP-1 increased 3.4-fold more rapidly in men (Te) than women (E2); and 3) end-infusion free IGF-I was 1.6-fold higher in men than women. In summary, E2, compared with Te supplementation, lowers concentrations of total and ultrafiltratably free IGF-I and elevates those of IGFBP-1 and binary IGF-I/IGFBP-1, thus putatively limiting IGF-I bioavailability. If free IGF-I mediates certain biological actions, then exogenous Te and E2 may modulate the tissue effects of total IGF-I concentrations unequally.

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Insulin-like growth factors (IGF)-I and -II and IGF binding protein-1, -2, and -3 in patients with acromegaly before and after adenomectomy

Metabolism ◽

10.1016/0026-0495(94)90199-6 ◽

1994 ◽

Vol 43 (5) ◽

pp. 579-583 ◽

Cited By ~ 25

Author(s):

Jens O.L. Jørgensen ◽

Niels Møller ◽

Jens Møller ◽

Jorgen Weeke ◽

Werner F. Blum

Keyword(s):

Growth Factors ◽

Binding Protein ◽

Igf I ◽

Before And After ◽

Igf Binding ◽

Igf Binding Protein ◽

Insulin Like Growth Factors

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Discontinuation of estrogen replacement therapy in GH-treated hypopituitary women alters androgen status and IGF-I

Acta Endocrinologica ◽

10.1530/eje.1.01898 ◽

2005 ◽

Vol 152 (5) ◽

pp. 719-726 ◽

Cited By ~ 10

Author(s):

Jens Juel Christiansen ◽

Sanne Fisker ◽

Claus Højbjerg Gravholt ◽

Paul Bennett ◽

Birgit Svenstrup ◽

...

Keyword(s):

Menopausal Status ◽

Free Testosterone ◽

Sex Hormone Binding Globulin ◽

Control Group ◽

Estrogen Replacement ◽

Igf I ◽

Igf Binding ◽

Igf Binding Protein ◽

Healthy Females ◽

Igfbp 3

Objective and design: Compared with their male counterparts, healthy females secrete more growth hormone (GH) and those with GH-deficiency have lower insulin-like growth factor I (IGF-I) levels and are less responsive to GH substitution. To test whether this gender difference is related to sex hormones we measured androgen status and IGF-I related parameters in 38 hypopituitary women (mean (range) age 41.5 (20–58) years) during continued GH substitution as compared with a control group of 38 healthy women matched for age and menopausal status. Twenty six patients were studied twice: with estrogen replacement and after 28 days of estrogen discontinuation in a randomised design. Results: The patients were androgen deficient compared with controls (median, range), dehydroepiandrosterone sulphate (DHEAS): 185 (99–7800) nmol/l vs 4400 (820–13 000) nmol/l, P = < 0.001; androstenedione: 0.5 (0.1–7.1) nmol/l vs 4.3 (1.6–8.8) nmol/l, P = < 0.001; dihydrotestosterone (DHT): 0.13 (0.09–0.54) nmol/l vs 0.55 (0.09–0.89) nmol/l, P = < 0.001; testosterone: 0.28 (0.09–1.56) nmol/l vs 1.1 (0.71–2.24) nmol/l, (P = < 0.001); free testosterone: 0.004 (0.001–0.030) nmol/l vs 0.016 (0.001–0.030) nmol/l, P = < 0.001. The circulating levels of IGF-I, IGF-II, IGF-binding protein 1 (IGFBP-1), and IGFBP-3 did not differ between patients and controls. The subgroup of patients receiving hydrocortisone (HC) replacement (n = 24) had significantly lower levels of androgens (suppressed by 80–100%) as well as IGF-I and IGFBP-3 as compared with the patients not receiving HC. IGF-I was correlated to free testosterone in patients (r = 0.57, P = 0.0005) as well as controls (r = 0.43, P = 0.008), and free testosterone was a significant positive predictor of IGF-I. Estrogen discontinuation induced an increase in IGF-I (167 ± 15 vs 206 ± 14 μg/l, P = 0.005 and IGFBP-3 (3887 ± 139 vs 4309 ± 138 μg/l, P = 0.0005). Estrogen discontinuation was associated with a significant increase in median (range) free testosterone (0.004 (0–0.02) vs 0.0065 (0–0.03) nmol/l, P = 0.001) and a significant decrease in median (range) sex-hormone binding globulin (SHBG; 93 (11–278) vs 55.5 (20–142) nmol/l, P = 0.001). ΔIGF-I correlated with ΔSHBG (r = −0.45 P = 0.033) and ΔIGFBP-3 (r = 0.67 P = < 0.001). In a regression model ΔE2, Δtestosterone, ΔSHBG and ΔIGFBP-3 explained 93% of the variation in ΔIGF-I. Conclusions: Androgen levels are low in hypopituitary women and free testosterone correlates with IGF-I. Discontinuation of estrogen replacement in these patients induces elevations in IGF-I as well as free testosterone, and ΔIGF-I correlated positively with Δfree testosterone. These effects may contribute to the gender differences observed in the GH–IGF axis in healthy adults as well as in the responsiveness of hypopituitary patients to GH substitution.

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