Plasma corticotropin-releasing hormone, corticotropin, and endorphins at rest and during exercise in eumenorrheic and amenorrheic athletes.

The hypothalamic-pituitary response to exercise was studied in 12 amenorrheic and in 9 eumenorrheic athletes by comparing the concentrations of corticotropin-releasing hormone (CRH), corticotropin (ACTH), and endorphins (beta-endorphin + beta-lipotropin) in plasma at rest and during an acute exercise on a bicycle ergometer requiring 80% and 100% of the maximal oxygen uptake (VO2 max). Plasma CRH levels did not change during the exercise, and the mean CRH values did not differ between the amenorrheic and eumenorrheic groups. In both groups, significant increases in the response to exercise were found in the concentrations of ACTH and endorphins. The only significant difference between the groups was a larger mean pre-exercise concentration of endorphins in amenorrheic than in eumenorrheic athletes (4.8 +/- 0.8 standard error [SE] and 2.9 +/- 0.2 pmol/l, respectively). It is concluded that in amenorrheic athletes the capacity of the anterior pituitary to secrete ACTH and endorphins in response to exercise does not significantly differ from that in eumenorrheic athletes, although basal endorphin secretion may be increased.