Rethinking gonadotropin releasing hormone agonist suppression test: why it should be a gonadotropin releasing hormone...

The gonadotropin-releasing hormone (GnRH) suppression test has traditionally used GnRH agonists to differentiate gonadotropin-dependent from gonadotropin-independent sex steroid production. Although physiologically sound, this approach is limited by an initial luteinizing hormone and follicle-stimulating hormone (FSH) flare and the prolonged interval required to achieve pituitary suppression. We revisit the physiologic basis of the traditional GnRH agonist suppression test and propose the hypothesis that GnRH antagonists may provide a more direct pharmacologic approach to diagnostic suppression testing. Unlike GnRH agonists, antagonists produce immediate competitive receptor blockade without an initial stimulatory flare, resulting in rapid suppression of pituitary gonadotropins. However, downstream testosterone and estradiol concentrations are expected to decline more gradually because of hormone synthesis and physiologic clearance. This modification, in theory, should be more efficient for suppression testing. However, the optimal timing of downstream hormone reassessment remains unknown and requires prospective clinical investigation. Antagonist-based suppression testing should therefore be regarded as a hypothesis-generating concept rather than an established clinical strategy. If prospectively validated, it may provide a practical refinement of conventional GnRH agonist-based suppression testing while preserving its physiologic foundation.