GnRH agonists vs antagonists: differences and add-back therapy?

GnRH agonists and antagonists both suppress estrogen to reduce endometriosis-driven inflammation and pain, but they do it differently. Antagonists typically work quickly and are taken orally, while agonists are usually given by injection and can cause a short initial “flare” in symptoms before full suppression occurs. The choice often depends on how fast suppression is needed, how a medication is taken, and your past response to hormonal therapies.

Add-back therapy is a small dose of hormone—often a progestin alone or combined low-dose estrogen/progestin—used alongside GnRH medications to reduce low-estrogen side effects. It’s primarily intended to help protect bone density and improve symptoms like hot flashes and sleep disruption, without significantly undermining pain control for many patients. Because these medications can carry meaningful side effects and aren’t a long-term solution for everyone, our team focuses on a careful, individualized risk–benefit discussion and where this fits in a broader treatment plan—reach out if you’d like to review options with us.