The Hormonal Response of Women During Sub-maximal and Maximal Exercise
There are successions of physiological responses that occur due to exercise, including the hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system activation. The stimulation of the HPA axis and the sympathetic nervous system secretes hormones that maintain the demands of muscles during exercise (Galliven 1997, Singh 1998). Activation of the HPA axis is demonstrated by the increase in elevated plasma levels of adrenocorticotropin (ACTH) and cortisol (Singh, 1999).
According to Singh et al (1999), there is a well-documented rise in ACTH in the early morning, which leads to relatively high cortisol levels at this time rather than in the evenings. However, Galliven (1997) found that metabolic and pituitary-adrenal response to either high- or moderate-intensity exercises are not effected in the AM or PM, despite the high levels of ACTH in the mornings. DeSouza (1991) found that both eumenorrheic and ammenorrheic athletes demonstrated similar ACTH baseline and response following submaximal and maximal exercise. This response considers the sensitivity of the neuroendocrine system to the level of the pituitary from the physiological stimulus due to exercise.
Singh (1999) noted a significant association between ACTH and prolactin concentrations. According to Singh (1999), this may indicate that corticotropin-releasing hormone (CRH), which regulates ATCH secretion, may also mediate the release of prolactin, as well. Significant increases in post-exercise plasma prolactin concentrations have also been noted in eumenorrheic runners (Singh, 1999). Prolactin is responsible for mobilizing fatty acids during exercise, which indicates it may participate in regulating energy usage by muscles during exercise (Singh 1999).
Interestingly, DeSouza (1991) states that the mild hypercortisolism reported in ammenorrheic athletes may indicate that the HPA axis may participate in ovarian suppression. During moderate and intense exercise in eumenorrheic athletes, the enhanced release of cortisol by the adrenal gland surpasses the uptake by working muscles, causing levels to rise (DeSouza, 1991). However, DeSouza (1991) observes that in ammenorrheic athletes, cortisol levels to not increase after submaximal or maximal exercise. This may be because pre-exercise cortisol levels are already elevated to the peak levels observed post-exercise in eumenorrheic athletes and may indicate reduced adrenal responsiveness in these athletes (DeSouza, 1991).
The prolactin levels of ammenorrheic runners were blunted by 50% compared to the eumenorrheic counterparts, during the follicular phase of the menstrual cycle. This difference for the prolactin response to exercise appears to be due to the steroid environment during this phase of the menstrual cycle (DeSouza, 1991).
Hormonal responses can be observed in both eumenorrheic and ammenorrheic athletes, however the ammenorrheic athlete demonstrates variations. These variations may be due to the mild rise of pre-exercise cortisol levels and a reduced responsiveness of the adrenal gland during exercise.
References
DeSouza, M.J., Maguire, M.S., Maresh, C.M., Kraemer, W.J., Rubin, K.R., and Loucks, A.B. (1991). Adrenal Activation and the Prolactin Response to Exercise in Eumenorrheic and Ammenorrheic Runners. J. Appl. Physiol. 70 (6): 2298-303.
Galliven, E.A., Singh, A., Michelson, D., Bina, S., Gold, P.W., and Deuster, P.A. (1997). Hormonal and Metabolic Responses to Exercise across Time of Day and Menstrual Cycle Phase. J. Appl. Physiol. 83 (6): 1822-1831.
Singh, A., Papanicolaou, D.A., Lawrence, L.L., Howell, E.A., Chrousos, G.P., and Deuster, P.A. (1999). Neuroendocrine Responses to Running in Women after Zinc and Vitamin E Supplementation. Med. Sci. in Sports & Ex. 31 (4): 536-42.