Obstetrics & Gynaecology/GnRH analoguelow yield

GnRH analogues

also: goserelin · leuprorelin · triptorelin · cetrorelix · Zoladex

Overview

Create a reversible "medical menopause". Agonists downregulate the pituitary after an initial flare; antagonists suppress immediately. Used in endometriosis, fibroids and assisted conception.

Mechanism

GnRH AGONISTS (goserelin/leuprorelin/triptorelin/buserelin): continuous, non-pulsatile receptor stimulation first causes a "flare" (transient ↑FSH/LH) then downregulates/desensitises pituitary GnRH receptors → ↓FSH/LH → hypogonadism. GnRH ANTAGONISTS (cetrorelix/ganirelix) competitively block the receptor → immediate suppression with NO flare.

Indications

Endometriosis (symptom control)
Uterine fibroids — shrink before surgery (with iron)
IVF pituitary suppression
Precocious puberty; also prostate & breast cancer (cross-reference)

The agents

Goserelin (Zoladex)agonist implant

SC depot 3.6/10.8 mg

Flare effect; depot.

Leuprorelin / Triptorelinagonist

depot

As goserelin.

Buserelinagonist

nasal/SC

Cetrorelix / Ganirelixantagonist

IVF — prevents premature LH surge, no flare.

Adverse effects

Menopausal symptoms (hot flushes, vaginal dryness, mood)classic

Reduced bone mineral densityserious

Limits use >6 months — give "add-back" HRT.

Initial symptom flare (agonists)common

Transient worsening in first weeks; relevant in prostate cancer (anti-androgen cover).

Cautions & contraindications

Pregnancypregnancy

Undiagnosed vaginal bleedingall

Osteoporosis (prolonged use)all

BMD loss — add-back HRT.

Interactions

Monitoring & kinetics

Bone density if >6 months; add-back HRT to protect bone + control vasomotor symptoms

Depot injections/implants (agonists); daily SC (antagonists).

Source: BNF — Gonadorelin analogues · NICE NG73 — Endometriosis