The purpose of this clinical trial is to see if intrauterine growth hormone infusions can help subjects reach a suitable endometrial thickness in patients who are resistant to routine hormonal therapy for embryo transfer in the In Vitro Fertilization (IVF) cycle.

The primary aim of this study is to assess the effectiveness of injecting Growth hormone directly into the uterus to enhance endometrial thickness. Additionally, we aim to compare the likelihood of pregnancy between patients receiving the Growth hormone infusion and those receiving a placebo.

Infertility impacts approximately 10-15% of couples globally, with over 1 million couples affected in Iran alone, adversely affecting their quality of life. However, Assisted Reproductive Technology (ART), notably In Vitro Fertilization (IVF), has markedly enhanced fertility outcomes for couples facing infertility.

The primary reason for IVF failure is often attributed to difficulties with embryo implantation. A crucial determinant in preparing the uterus for successful implantation is achieving an adequate endometrial thickness. A thin endometrium, typically defined as less than 7 mm in thickness, is associated with a significantly reduced likelihood of successful pregnancy following implantation. As a result, patients with thin endometrium are often deemed unsuitable candidates for implantation.

Despite exploring various pharmacological options, certain patients remain unable to achieve the minimum required endometrial thickness for successful implantation. Prior investigations have examined the impact of subcutaneous growth hormone injections on endometrial thickness in individuals with thin endometrium, yielding mixed results across studies. Direct infusion of drugs into the uterine cavity presents a potential route for localized treatment, thereby minimizing systemic effects under specific circumstances. Thus, different studies explored the possible intra-uterine effect of drugs such as Granulocyte colony stimulating factor (GCSF), and Human chorionic gonadotropin (hCG). To date, only an animal study and two small studies without control group have investigated the efficacy of direct intrauterine infusion of growth hormone in increasing endometrial thickness among patients with thin endometrium. However, the absence of randomized controlled trials with placebo groups limits our understanding of the effectiveness of intrauterine growth hormone therapy in this patient population. Thus, we aimed to design an exploratory randomized clinical trial with parallel placebo group to evaluate the effectiveness of intrauterine Growth Hormone infusion as an add-on therapy to conventional hormone therapy compared to placebo in patients with thin endometrium undergoing frozen thawed embryo transfer

Inclusion Criteria:

• At least a history of cycle cancellation due to a thin endometrium less than 7 mm following standard hormonal treatment
• Availability of ≥1 embryo with good quality
• Normal baseline hormones value including: Testosterone, Progesterone, Prolactin, Luteinizing Hormone (LH), Follicle Stimulating Hormone (FSH)

Exclusion Criteria:

• Internal genital anomalies
• Active intrauterine infection Endometrial thickness≥7 on the 10th day of menstrual cycle
• History of Asherman syndrome
• History of cancer
• History of uterine surgery in past 3 months
• Intrauterine polyps visible in Transvaginal Ultrasonography
• Visible intrauterine adhesion
• Pathospermia in partner
• Premature ovarian failure

Individual Participant Data (IPD) may be shared following the publication of the study, as per specific requests from the researchers.

In this study, a double-blind methodology will be employed to minimize bias. Patients will be administered medication without knowing the study group and placebo or treatment intervention. To ensure uniformity between growth hormone and placebo, which has a similar appearance to the placebo, will be prepared by an individual informed of the enrolled patients in the study and will be provided to the administering physician. The evaluator assessing outcomes such as clinical pregnancy rate and endometrial thickness will not know which treatment each patient received. Laboratory staff will also be unaware of the treatment groups.