Subcutaneous administration of gonadotropin-releasing hormone: Absorption kinetics and gonadotropin responses

Abstract

To evaluate the suitability of the sc route for the pulsatile delivery of GnRH, plasma GnRH, LH, and FSH levels were measured by RIA in five women with hypothalamic amenorrhea after sc injection of single doses of 2.5, 5, and 10 μg GnRH. The results were compared with those obtained after bolus iv injection of 10 μg GnRH. After sc injection, plasma GnRH levels rose to a dose-related maximum after 5-10 min and fell to less than 10% of the peak value by 90 min. The mean plasma disappearance half-time was 24 min (range, 18-30 min). After bolus iv injection, an initial rapid phase of disappearance (t½, 2.8 min) was followed by a slower phase (t½, 33 min), falling within the 95% confidence interv..