Plasma concentrations of beta-endorphin in trained eumenorrheic and amenorrheic women.
OBJECTIVE
To characterize the pattern of plasma beta-endorphin throughout the normal menstrual cycle and test the hypothesis that beta-endorphin concentrations are elevated in trained women with amenorrhea compared with trained and sedentary eumenorrheic women.


METHODS
Cohort analytic study.


METHODS
Academic research environment.


METHODS
Healthy female volunteers: 10 eumenorrheic sedentary, 11 eumenorrheic trained, and 11 amenorrheic trained women.


METHODS
Blood samples were collected three times per week for either one complete menstrual cycle (eumenorrheic sedentary and trained subjects) or for a 4-week period (amenorrheic trained subjects).


METHODS
Plasma beta-endorphin concentrations.


RESULTS
beta-Endorphin levels varied considerably across the sampling period and were not associated with menstrual status, gonadotropin, or gonadal steroid concentrations. Average beta-endorphin levels were not different between the follicular and luteal phases for menstruating subjects, but were greater in the eumenorrheic athletes. Compared with eumenorrheic sedentary subjects, plasma beta-endorphin levels were higher in the athletic groups, regardless of menstrual status.


CONCLUSIONS
There were no cycle-related beta-endorphin changes. Eumenorrheic and amenorrheic athletes have higher beta-endorphin concentrations that may reflect adaptations to intense training and not exercise-associated amenorrhea.
Harber
V J
VJ
Department of Reproductive Biology, McMaster University, Hamilton, Ontario, Canada. vharber@per.ualberta.ca
Sutton
J R
JR
MacDougall
J D
JD
Woolever
C A
CA
Bhavnani
B R
BR
D000328:Adult; D000568:Amenorrhea / Q000097:blood*; D015331:Cohort Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D012739:Gonadal Steroid Hormones / Q000097:blood; D006065:Gonadotropins, Pituitary / Q000097:blood; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood; D008597:Menstrual Cycle / Q000097:blood*; D011388:Prolactin / Q000097:blood; D012146:Rest / Q000502:physiology; D001615:beta-Endorphin / Q000097:blood*
D012739:Gonadal Steroid Hormones; D006065:Gonadotropins, Pituitary; D001615:beta-Endorphin; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone