title: The effect of increased cardiac output on luteal phase gonadal steroids: a hypothesis for runners amenorrhea.
abstract: The beta-adrenergic agonist isoproterenol was infused intravenously for 4 hours during the midluteal phase of the cycle in six normal women. A rapid increase in cardiac output occurred for the entire duration of the isoproterenol infusion and serum estrogen and progesterone levels (but not luteinizing hormone levels) decreased significantly (P less than 0.001) to a nadir of 30% and 50% of baseline levels, respectively, suggesting increased metabolic clearance of the two steroids. We hypothesize that endurance training chronically increases metabolic clearance of gonadal steroids, resulting in abnormal negative and/or positive feedback on the hypothalamic/pituitary axis leading to the menstrual irregularities commonly seen in athletes.
mesh_terms: D000328:Adult; D000568:Amenorrhea / Q000209:etiology* / Q000503:physiopathology; D002302:Cardiac Output / Q000187:drug effects; D004967:Estrogens / Q000097:blood*; D005260:Female; D006801:Humans; D007263:Infusions, Parenteral; D007545:Isoproterenol / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood; D008954:Models, Biological; D011374:Progesterone / Q000097:blood*; D012420:Running
chemical_list: D004967:Estrogens; D011374:Progesterone; D007986:Luteinizing Hormone; D007545:Isoproterenol