Effect of sex steroids on beta-endorphin levels at rest and during submaximal treadmill exercise in anovulatory and ovulatory runners

Objective: To examine the interaction between circulating beta-endorphin le vels and sex steroids during sustained submaximal exercise in runners who a re either anovulatory and oligomenorrheic (AO) or ovulatory and eumenorrhei c (EO). Design: Controlled clinical study. Setting: General clinical research center at an academic medical center. Patient(s): Three AO and four EO runners. Intervention(s): The athletes underwent 60 minutes of submaximal treadmill exercise on three separate occasions. Anovulatory and oligomenorrheic runne rs underwent exercise at baseline and after physiologic estrogen and combin ed estrogen and progesterone replacement. Ovulatory and eumenorrheic runner s underwent exercise in the follicular and luteal phases and after GnRH ago nist desensitization. Main Outcome Measure(s): Serum cortisol, beta-endorphin, progesterone, estr ogen, and gonadotropin levels at rest and during exercise. Result(s): Serum levels of E-2 increased in response to exercise in both EO and AO runners during sex steroid replacement, Baseline peripheral beta-en dorphin and cortisol levels were not different between the EO and AO groups . A significant increase in beta-endorphin levels in response to exercise o ccurred only in the EO group after GnRH agonist desensitization. Conclusion(s): Alterations in menstrual cyclicity and ovulation in conditio ned runners probably are not due to an increase in opioid tone. The hypotha lamic-gonadotropic axis appears to be intact in AO runners, as measured by the gonadotropic response to exogenous exposure-to estrogen and progesteron e. Sex steroid administration had no effect on basal beta-endorphin levels, but this probably was not due to preexisting increased opioid tone. (Ferti l Steril(R) 1999;71:1085-91. (C) 1999 by American Society for Reproductive Medicine.).