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

Abstract

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.

The effect of exercise duration and mode on the growth hormone responses in young women on oral contraceptives

“…Consistent with Felsing's findings (Felsing et al 1992), these data revealed an absolute increase in GH levels of 9.5 ngAEml )1 for the 10-min exercise bout on the cycle ergometer, while it demonstrated an absolute increase of 5.7 ngAEml )1 on the treadmill. This increase in GH levels is similar to increases in GH seen in exercise protocols using a single bout of exercise of longer duration in women (Bunt et al 1986;Wideman et al 1999), while these increases appear to be somewhat smaller than what Bernardes and Radomski (1998) found in women on oral contraceptives. The earlier work by Felsing showed no significant increase with 1 and 5 min of exercise.…”

“…Oral contraceptive use has been shown to be related to these higher resting GH concentrations (Bonen et al 1983). Oral contraceptive users have been shown to have an appropriate GH response to exercise (Bemben et al 1992;Bernardes and Radomski 1998;Bonen et al 1983) and in our study 10 min of exercise also stimulated a significant GH response. However we found a decline in GH levels with subsequent exercise bouts and have no explanation for this since it deviates from what is reported to occur in men (Kanaley et al 1997).…”

“…Mishell and associates (1977) examined the effects of contraceptive steroids on the hypothalamic-pituitary function and concluded that oral contraceptive use directly affects the pituitary as well as the hypothalamus resulting in gonadotropin suppression. If the hypothalamus is the major site of action of contraceptive steroids, then it seems likely that oral contraceptive use may also have an effect on the release of GH (Bernardes and Radomski 1998), since regulation is believed to be controlled by the hypothalamus (Luger et al 1992). Therefore, resting GH levels may be affected by the use of oral contraceptive when subsequent bouts of exercise are performed.…”

“…Most exercise-induced GH research has focused primarily on men (Felsing et al 1992;Hagberg et al 1988;Hornum et al 1997;Kanaley et al 1997Kanaley et al , 2001Karagiorgos et al 1979;Lassarre et al 1974;Pritzlaff et al 1999;Thompson et al 1993;VanHelder et al 1984VanHelder et al , 1986Weltman et al 1997;Zaccaria et al 1999), with very few studies focusing on women (Bernardes and Radomski 1998;Bonen et al 1983;Bunt et al 1986;Wideman et al 1999), primarily because of the confounding effects of the menstrual cycle. Women are known to have higher basal GH concentrations than men and this is believed to be due to higher estrogen levels in women ( Van den Berg et al 1996).…”

Ausência de variação da flexibilidade durante o ciclo menstrual em universitárias

“…A progesterona não respondeu de forma significativa quanto à fase do CM ou o tipo de exercício. Essa aumentou durante os dois tipos de exercício em todas as condições do ciclo e retornou aos valores de pré-exercício 60 minutos depois de cessado o mesmo 17 .…”