Appropriate Castration with Luteinising Hormone Releasing Hormone (LHRH) Agonists: What is the Optimal Level of Testosterone?

Abstract

Traditionally serum testosterone castration levels were set at a minimum of 50 ng/dL. Achieving and maintaining these castration levels are the main goal of therapy with luteinising hormone releasing hormone (LHRH) agonists. As the optimal castration level remains debated, this paper aims to review published literature challenging the 50 ng/dL definition, as well as studies evaluating the effects of LHRH agonists on testosterone suppression. A Medline search was performed in the last quarter of 2004. Only fully published studies and review articles in English language were included. The threshold of 50 ng/dL has been set arbitrarily, based on the available measuring techniques. As those techniques are developed in the late 1960s and current techniques are more accurate, this article discusses elements for defining an appropriate castration as achieving testosterone levels below 20 ng/dL. Ideally, chemical castration with LHRH agonists should achieve similar testosterone levels as those obtained with orchiectomy (15 ng/dL). As a consequence, using orchiectomy as a benchmark would favour 20 ng/dL over 50 ng/dL as a cut-off point for appropriate castration. LHRH agonists have been thought to achieve an almost 100% of response in the initial therapy. Several studies have shown that when using a more stringent definition of castration, treatment with current LHRH agonists does not achieve this goal. As a consequence, measurement of testosterone should regain attention for evaluating treatment response to LHRH agonists as well as for monitoring breakthroughs and acute-on-chronic responses.