🔬 Fibroid GnRH Agonist Shrinkage Simulator

Large Symptomatic Fibroid With Bleeding Anemia

A large uterine fibroid drives heavy menstrual bleeding and anemia.

• 150–500 cm³: Typical fibroid volume (large intramural myoma)
• 7–9 g/dL: Baseline hemoglobin (moderate to severe anemia)
• >80 mL: Cyclic blood loss (per menstrual cycle)
• ~70%: US prevalence by age 50 (women, any race)

Fibroid growth is estrogen-driven

Estrogen and progesterone fuel myoma cell proliferation.

Bleeding source is endometrial surface

Enlarged fibroids distort and enlarge the bleeding surface.

Anemia raises surgical risk

Low hemoglobin increases transfusion and complication rates.

Preoperative anemia correction is a core goal of GnRH pretreatment.

GnRH Agonist Flare, Then Sustained Suppression

Leuprolide first stimulates, then desensitizes the pituitary-ovarian axis.

• 1–2 wks: Flare duration (transient estrogen surge)
• ~2–3 wks: Downregulation onset (pituitary desensitization)
• ~95%: Peak suppression (castrate-level estrogen)
• days: Elagolix onset (direct antagonist, no flare)

Agonists cause an initial flare

Leuprolide briefly boosts LH, FSH, and estrogen release.

Receptors then downregulate

Continuous stimulation desensitizes pituitary GnRH receptors.

Flare bleeding can worsen briefly before suppression takes hold.

Antagonists skip the flare

Elagolix blocks receptors immediately, no surge phase.

Fibroid Shrinkage Under Estrogen Deprivation

Low estrogen starves fibroid tissue, shrinking it over weeks.

• 35–45%: Agonist shrinkage at 12 wks (volume reduction)
• 15–20%: Elagolix combo shrinkage (partial add-back therapy)
• ~2–3 wks: Shrinkage onset (after suppression begins)
• ~8–10 wks: Plateau reached (diminishing further shrinkage)

Vascular supply contracts first

Reduced estrogen shrinks the fibroid blood supply early.

Cell proliferation slows

Myoma cell division and matrix turnover both decline.

Add-back limits shrinkage

Elagolix combination preserves some estrogen, capping shrinkage.

Full agonist therapy shrinks fibroids more than combination regimens.

Anemia Correction As Bleeding Subsides

Suppressed bleeding lets bone marrow rebuild hemoglobin stores.

• ~60–80%: Amenorrhea rate (by week 8 of therapy)
• +2–4 g/dL: Hemoglobin gain (over 8–12 weeks)
• concurrent: Iron repletion (oral or IV supplementation)
• ≥12 g/dL: Target pre-op Hb (reduces transfusion need)

Amenorrhea stops ongoing loss

No menstrual bleeding means no further iron loss.

Marrow response takes weeks

Hemoglobin rises gradually, not immediately after amenorrhea.

Iron supplementation accelerates hemoglobin recovery alongside GnRH therapy.

Regimen affects recovery speed

Elagolix combination controls bleeding faster than agonist flare.

Optimized Candidate For Fibroid Surgery

Smaller fibroid and corrected anemia make surgery markedly safer.

• ~40%: Blood loss reduction (intraoperative, vs untreated)
• ~50%: Transfusion rate drop (with preoperative therapy)
• shorter: Operative time (smaller mass, less vascularity)
• 8–12 wks: Recommended duration (before scheduled surgery)

Smaller mass eases dissection

A shrunken fibroid simplifies myomectomy or hysterectomy.

Corrected anemia lowers risk

Higher hemoglobin reduces transfusion and complication rates.

Timing the surgical window

Surgery is scheduled near peak shrinkage and hemoglobin.

Combining both benefits yields the safest operative window.