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

Abstract

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...

The GH-IGF-I Response to Typical Field Sports Practices in Adolescent Athletes: A Summary

“…Similarly, an increase of other hormones, that may mediate the GH response, like catecholamines, cortisol and inflammatory cytokines, also occurs only or mainly during exercise above the LAT (12). More recently it was shown that increases in exercise intensity (25%, 75%, 100%, 125%, and 175% of LAT) during constant exercise resulted in increased GH secretion in a linear dose-dependent manner (17). Consistent with that, percent changes in GH secretion were not related to changes in lactate levels following the different typical field practice sessions in the current study.…”

“…Gender-related differences in the GH response were examined mainly following aerobic exercise. It was shown that both genders have a similar pattern of exercise-related GH response (17,25), but females reach peak GH concentrations sooner (26). During constant exercise duration, GH secretion is related to exercise intensity in a linear dose-dependent fashion.…”

“…During constant exercise duration, GH secretion is related to exercise intensity in a linear dose-dependent fashion. However, at any given exercise intensity (eg, below and above the lactic anaerobic threshold-LAT), females had higher GH concentrations (17). Interestingly, these gender differences disappeared when endurance exercise was performed intermittently (23), and were diminished with age (22).…”

Hormônio do crescimento e exercício físico: considerações atuais

“…Entre 40 e 60 min de atividade, a concentração basal ou de repouso do GH, que é de 1-2 µg/L, pode aumentar em diversas vezes, sendo a amplitude deste aumento dependente da intensidade em que o exercício físico for realizado (Felsing, Brasel, Cooper, 1992). Embora em alguns estudos a concentração do GH tenha variado entre 5-25 µg/L na intensidade leve a moderada (25% a 75% VO 2máx ) (Pritzlaff et al, 1999;Marcell et al, 1999;Pritzlaff et al, 2002) Marcell et al, 1999;Zaccaria et al, 1999;Weltman et al, 2006. Intensidade Liberação aumenta de acordo com a intensidade Bonifazi et al, 1998;Ehrnborg et al, 2003;Kanaley et al, 1997;Pritzlaff et al, 1999;Wideman et al, 1999.…”

“…Além disso, independentemente do estado de treinamento, mulheres no início de uma atividade podem apresentar liberação mais rápida de GH, ao passo que ao término da sessão a depuração de GH pode ser reduzida quando comparada aos resultados obtidos em homens (Bunt et al, 1986). Diversos trabalhos vêm estabelecendo escalas de referência diferentes para cada gênero nas concentrações de GH, IGF-1 e outros marcadores de colágeno e crescimento ósseo Pritzlaff et al, 2002;Ehrnborg et al, 2003).…”