Intersubject viability in growth hormone time course during different types of work

Raynaud, Julien; Capderou, André; Martineaud, J.P.; Bordachar, J; Durand, Jean-Bernard

doi:10.1152/jappl.1983.55.6.1682

Cited by 53 publications

(29 citation statements)

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“…Other studies also observed that exercise-induced GH concentrations peak at or near the end of exercise (16,22). Likewise, as previously noted with exercise (5,16,22,24,33) and other stimulation tests (8,25), we observe considerable intersubject variability in peak serum GH values.…”

supporting

confidence: 89%

Gender governs the relationship between exercise intensity and growth hormone release in young adults

Pritzlaff-Roy¹,

Widemen²,

Weltman³

et al. 2002

Journal of Applied Physiology

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We previously reported that in young adult males growth hormone (GH) release is related to exercise intensity in a linear dose-response manner (Pritzlaff et al. J Appl Physiol 87: 498-504, 1999). To investigate the effects of gender and exercise intensity on GH release, eight women (24.3 Ϯ 1.3 yr, 171 Ϯ 3.2 cm height, 63.6 Ϯ 8.7 kg weight) were each tested on six randomly ordered occasions [1 control condition (C), 5 exercise conditions (Ex)]. Serum GH concentrations were measured in samples obtained at 10-min intervals between 0700 and 0900 (baseline) and 0900 and 1300 (Ex ϩ recovery or C). Integrated GH concentrations (IGHC) were calculated by trapezoidal reconstruction. During Ex, subjects exercised for 30 min (0900-0930) at one of the following intensities [normalized to the lactate threshold (LT)]: 25 and 75% of the difference between LT and rest, at LT, and at 25 and 75% of the difference between LT and peak O2 uptake. No differences were observed among conditions for baseline IGHC. To determine whether total (Ex ϩ recovery) IGHC changed with increasing exercise intensity, slopes associated with individual linear regression models were subjected to a Wilcoxon signed-rank test. To test for gender differences, data in women were compared with the previously published data in men. A Wilcoxon ranked-sums two-tailed test was used to analyze the slopes and intercepts from the regression models. Total IGHC increased linearly with increasing exercise intensity. The slope and intercept values for the relationship between total IGHC and exercise intensity were greater in women than in men. Deconvolution analysis (0700-1300 h) revealed that, regardless of gender, increasing exercise intensity resulted in a linear increase in the mass of GH secreted per pulse and summed GH production rate, with no changes in GH secretory pulse frequency or apparent half-life of elimination. Exercise reduced the half-duration of GH secretory burst in men but not in women. Gender comparisons revealed that women had greater basal (nonpulsatile) GH secretion across all conditions, more frequent GH secretory pulses, a greater GH secretory pulse amplitude, a greater production rate, and a trend for a greater mass of GH secreted per pulse than men. We conclude that, in young adults, the GH secretory response to exercise is related to exercise intensity in a linear dose-response pattern. For each incremental increase in exercise intensity, the fractional stimulation of GH secretion is greater in women than in men. male; female; lactate threshold; endocrinology; pituitary; somatotropin ACUTE EXERCISE IS A POWERFUL stimulus to growth hormone (GH) release (2-5, 15, 17, 20, 32, 33). Previous research has suggested that exercise intensity plays a key role, wherein a particular threshold of exercise intensity must be exceeded to elicit GH release (3-5). However, recent data from our laboratory indicate that, in young men, the magnitude of GH release rises with increasing exercise intensity in a linear doseresponse relationship (as opposed to a thre...

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supporting

confidence: 89%

Gender governs the relationship between exercise intensity and growth hormone release in young adults

Pritzlaff-Roy¹,

Widemen²,

Weltman³

et al. 2002

Journal of Applied Physiology

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“…Every eort was made to normalize as many factors as possible given the eect of circadian rhythms and the high inter-individual variability inherent in GH levels (Raynaud et al 1983). Since estrogen is Values for intermittent exercise are signi®cantly higher (P < 0.01) than for continuous exercise from t 4 to t 20 min known to stimulate GH secretion (Frantz and Rabkin 1965;Ho et al 1987), we hypothesized that a heightened GH response to exercise would occur during the OCU phase, when plasma levels of total estradiol (endogenous plus exogenous) would be elevated.…”

Section: Discussionmentioning

confidence: 99%

“…Conversely, other studies have reported that in female runners the incremental GH responses to exercise are not in¯uenced by menstrual phase (Kanaley et al 1992). These dierences in the literature may be partially attributable to dierences in exercise protocols, subject selection, and large intersubject variability in GH responses (Raynaud et al 1983).…”

Section: Introductionmentioning

confidence: 93%

Growth hormone responses to continuous and intermittent exercise in females under oral contraceptive therapy

Bernardes

Radomski²

1998

European Journal of Applied Physiology

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In this study we investigated the effect of oral contraceptive (OC) use (OCU) and non-use (OCNU) on growth hormone (GH) responses to exercise in the same females (n = 7, age 22-31 years) during the normal course of OC therapy. Continuous (60% maximum oxygen consumption, VO2max for 20 min) and intermittent exercise (>80% VO2max) protocols of equal total duration, and similar external work were performed during phases of OCNU (days 3-5 of the menstrual cycle) and OCU (days 7-11). Levels of GH, lactate, 17 beta-estradiol, and progesterone were measured. Lactate responses were significantly greater (P<0.05) during intermittent than continuous exercise, with no effect of OC use. However, significantly greater GH responses were found during the OCU phase than the OCNU phase in both the continuous (+94%) and intermittent (+250%) exercise protocols. Estradiol and progesterone levels increased significantly during exercise in all four conditions. We suggest that the increased GH responses observed during the OCU-phase were potentiated by the elevated levels levels of total estrogens (endogenous 17 beta-estradiol and exogenous ethinyl estradiol). It is suggested that training programs for female athletes could be timed in accordance with the menstrual cycle to benefit from an increased GH response to exercise during phases of OC use or the luteal phase of women not on OC therapy.

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“…The GH response increases with both duration (8) and intensity of exercise (9,10). It is likely that exercise stimulates GH secretion through similar pathways to those that operate in the resting state (see 11 for references), through the hypothalamic secretion of GHRH and somatostatin, which stimulate and inhibit GH release respectively.…”

Section: Introductionmentioning

confidence: 99%

Exercise-induced GH secretion is enhanced by the oral ingestion of melatonin in healthy adult male subjects

et al. 1999

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There is evidence that melatonin may play a role in modulating pituitary secretion, although the mechanisms are unclear. We examined the effects of a single dose of oral melatonin (5 mg) on exerciseinduced GH secretion. In a randomised, double-blind, placebo-controlled study, seven healthy male subjects undertook an initial period of graded bicycle ergometric exercise to determine maximum workload and oxygen uptake (VO 2 max ). Subjects were subsequently studied on two further occasions, receiving either melatonin or placebo in random order at the onset of each study (¹60 min). At 0 min a period of bicycle exercise was performed for 8 min at a workload corresponding to 70 % of that achieved at VO 2 max . Serum GH and IGF-binding protein-1 (IGFBP-1) concentration was measured at 15-min intervals from the onset of the study until 120 min post-exercise. Blood was also sampled for the measurement of plasma glucose, insulin, non-esterified fatty acids, IGFBP-3, melatonin and vasopressin concentration. There was an exercise-induced increase in GH concentration following melatonin which was greater compared with placebo as assessed by both area under the curve (P < 0.01) and peak increase in GH levels (P < 0.01). The peak increase in IGFBP-1 levels post-exercise was also significantly greater following melatonin compared with placebo (P < 0.01) but did not quite reach levels of significance as measured by area under the curve (P = 0.07). Since exercise-induced GH secretion is thought to be mediated predominantly through a hypothalamic pathway, it seems likely that melatonin facilitates GH secretion at a hypothalamic level.

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Intersubject viability in growth hormone time course during different types of work

Cited by 53 publications

References 0 publications

Gender governs the relationship between exercise intensity and growth hormone release in young adults

Gender governs the relationship between exercise intensity and growth hormone release in young adults

Growth hormone responses to continuous and intermittent exercise in females under oral contraceptive therapy

Exercise-induced GH secretion is enhanced by the oral ingestion of melatonin in healthy adult male subjects

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