A randomized controlled trial of intrauterine growth hormone for thin endometrium

Thin endometrium impairs assisted reproduction outcomes. Given the uncertain efficacy and safety profile of intrauterine Growth Hormone (GH) as a therapeutic intervention, this exploratory trial was designed to evaluate its role in treating patients with this condition. An add-on, randomized, double-blind, placebo-controlled trial was conducted. Participants were randomly assigned to receive either six international units of GH or placebo. The pre‑specified primary outcome was final endometrial thickness (ET). Secondary outcomes included biochemical pregnancy, clinical pregnancy, early miscarriage, and treatment response rate. Fifty-two patients were included in the per-protocol analysis, which served as the primary analysis for this exploratory trial. The analysis revealed no significant between-group difference in the final ET. Secondary analyses indicated that treatment response rates and the intensity of therapy required were comparable between groups. A numerical increase in biochemical pregnancy was observed with GH administration (47.6% vs. 23.8%; RD = 0.23, NNT = 4.2, p = 0.10), though the trial was not powered for this outcome. This did not translate into a statistically significant difference in clinical pregnancy rates. No ectopic pregnancies were reported. The administration of intrauterine GH did not result in a statistically or clinically meaningful improvement in ET. However, the observed numerical trend toward higher pregnancy rates, while not statistically significant, cannot exclude a possible biological effect that may warrant investigation in larger-scale trials. All pregnancy-related findings are exploratory and hypothesis-generating.Trial registration: This trial was registered on www.clinicaltrial.gov (NCT06379659) and the World Health Organization trial registry of IRAN (IRCT20110908007513N18).