One change seen in PC is with androgen receptor (AR) signalling. This is required for normal prostate development and function but PC can ‘hijack’ this.

An important aim, therefore, is to suppress androgens levels, especially testosterone. This chemical castration can slow, halt or even reverse prostate tumour progression and reduce PSA levels for months or years.³⁸

Luteinising hormone-releasing hormone (LHRH) agonists, gonadotropin releasing hormone (GnRH) analogues or LH blockers such as leuprorelin, goserelin, buserelin or triptorelin suppress testicular testosterone production.^39,40

After an initial stimulation of LH release by the pituitary gland, there is a down-regulation of the hypothalamic-pituitary-gonadal (HPO) axis. To avoid the risk of the temporary testosterone increase causing a tumour flare when starting the depot injections, patients will require a short course of bicalutamide or other anti-androgen started a few days before the first injection.⁴¹

Alternatively, the GnRH blocker degarelix may be used as there is no risk of tumour flare.⁴²