It has recently been found that prevention of the acidosis of anaerobic exercise blocks beta-endorphin release. Because heavy exercise affects secretion of other anterior pituitary hormones, we studied the results of alkali infusion and ingestion upon blood levels of four hormones: luteinizing hormone (LH), follicle-stimulating hormone (FSH), growth hormone (GH), and prolactin (PRL). Eight male subjects were studied after either 2 mEq/kg placebo (NaCl) or alkali (NaHCO3) administered before and during exercise to exhaustion. Blood samples were obtained before exercise and then 15, 30, 60, 90, 120, and 180 min postexercise. GH and PRL but not FSH or LH increased significantly postexercise, with a peak at 60 min, and subsequently declined back to baseline by 180 min. Base treatment reduced GH at baseline and postexercise (except at 60 min) and increased PRL significantly, particularly at 60 min. While the precise mechanisms on how acid/base changes affect hormone release remain to be defined, there are possible consequences on gonadal function and substrate availability during exercise.