Synthetic LRH was infused into normal women and women with obesity and anorexia nervosa to determine the distribution volume (DV), metabolic clearance rate (MCR) and half disappearance time (t 1/2) of plasma LRH. In normal women, the DV of LRH ws 12.1 +/- 0.9 (mean +/- SE) 1, the MCR was 1478.9 +/- 39.8 ml/min (28.5 +/- 1.2 ml/min/kg body weight) and the initial t 1/2 was 5.6 +/- 0.4 min. In obese patients the DV (20.6 +/- 1.5 l) was significantly higher than that in normal subjects (P < 0.005), but the MCR and t 1/2 were not significantly different from those in normal subjects. In patients with anorexia nervosa the DV and MCR were 6.5 +/- 1.1 l and 621.8 +/- 110.5 ml/min (17.9 +/- 2.4 ml/min/kg body weight), respectively, which were both significantly lower than those in normal subjects (P < 0.02), while the t 1/2 (7.3 +/- 0.1 min) was longer than in normal subjects (P < 0.02). These data suggest that 1) the abnormal responses of some hormones to provocation tests observed in obese patients and patients with anorexia nervosa should be evaluated in consideration of changes in the DV and metabolic clearance of hormones in these conditions, and 2) in patients with anorexia nervosa changes in MCR and t 1/2 may reflect low metabolism of LRH.