Glycemic Regulation as Endometriosis Adjunct Treatment (GREAT)

The goal of this pilot trial is to learn if a novel non-hormonal treatment, metformin hydrochloride, works to treat pelvic pain in young women with endometriosis. The main questions it aims to answer are:

• Is metformin superior to placebo in alleviating pain symptoms in young women with endometriosis?
• Does metformin alter systemic inflammatory markers over 6 months in young women with endometriosis?

Researchers will compare metformin to a placebo (a look-alike substance that contains no drug) to see if metformin works to treat pelvic pain.

Participants will:

• Take drug metformin or a placebo every day for 6 months
• Visit the clinic three times: once at baseline (pre-treatment), once at 3 months, and once at 6 months
• Keep a daily symptom diary to track pain, bleeding, and usage of any pain medications

Study Overview

• Status: Recruiting
• Conditions: Endometriosis; Pelvic Pain
• Intervention / Treatment: Drug: Placebo; Drug: Metformin Hydrochloride

Detailed Description

Endometriosis is a chronic illness defined by the presence of endometrial glands and stroma outside the uterine lining. While prevalence estimates vary depending on the population studied, endometriosis is thought to affect approximately one in ten reproductive aged women, up to 50% of women with infertility, and up to 70% of adolescents with chronic pelvic pain. Over 10 million women in the United States have endometriosis and incur significantly higher direct and indirect healthcare costs than those without. Annual health care costs are estimated at $100 billion in the United States alone. While the majority of patients report the onset of endometriosis symptoms during adolescence, delays in diagnosis are common and range from 7 to 12 years. During these delays, women may suffer from debilitating symptoms interfering with school and social activities, and commonly experience reduced health-related quality of life and work productivity. When left untreated, endometriosis can progress significantly in over 50% of patients and result in a higher stage of disease. Therefore, timely intervention and maintenance of therapy is critical for preventing the progression of disease and patient burden.

Therapeutic options for endometriosis include surgical and medical management. Because surgery is not curative, long-term medical therapy is often advised to prevent recurrence of symptoms and retard the progression of disease. Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used for endometriosis-related pain but do not remove or decrease deposits of ectopic endometrium. Hormonal therapies are the mainstay of medical therapy as they can inhibit prostaglandin production that contributes to pain, and cause decidualization and atrophy of ectopic endometrial tissue. Unfortunately, hormonal treatments have varied degrees of success and no data support one treatment over another. Additionally, the treatment choice may be limited to medication side effects, availability, costs, and contraceptive needs. Hormonal treatments do not cure endometriosis; 11-19% of women may not experience any relief with medical therapy, and up to a third of women experience recurrence of pain symptoms after treatment cessation. Additionally, as endometriosis is predominantly a disease of young reproductive-aged women, patients may desire a treatment with a different mechanism of action that does not impact ovarian function and fertility. There remains an unmet clinical need among women with endometriosis for effective and well-tolerated medical therapies.

Metformin, an insulin-sensitizing oral biguanide, is approved for the treatment of type 2 diabetes. Several published studies using in vitro and animal models have implicated metformin with a regression of endometriotic implants and reduction of inflammatory activity. Yet, the mechanisms of action of metformin remain to be further elucidated. Only one prospective study to date has investigated the use of metformin in humans as monotherapy for endometriosis; this study had substantial limitations. Further investigation will be improved with participant and provider blinding, use of validated pain measures, and inclusion of a broader population of patients affected by endometriosis. A randomized clinical trial is necessary to investigate the mechanisms and efficacy of metformin as an anti-endometriotic drug.

• Study Type: Interventional
• Enrollment (Estimated): 14
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Mari Garza, BA; Phone Number: 6173557648; Email: GYNResearch@childrens.harvard.edu
• Study Contact Backup: Name: Jessica Shim, MD; Phone Number: 6173557648; Email: GYNResearch@childrens.harvard.edu

Study Locations

• United States
  • Massachusetts
    • Boston, Massachusetts, United States, 02115
      • Recruiting
      • Boston Children's Hospital
      • Contact: Jessica Shim, MD; Phone Number: 6173557648; Email: Jessica.Shim@childrens.harvard.edu
      • Principal Investigator: Jessica Shim, MD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Female with surgically confirmed endometriosis, determined at laparoscopy
• Current use for at least 2 months duration of a consistent hormonal therapy for endometriosis (either combination hormonal contraceptives or progestin-only therapy)
• Current pelvic pain (score ≥ 3 on Visual Analog Scale) that has been present for at least 2 months prior to enrollment
• Age 15 years to 35 years and premenopausal
• Willingness to comply with visit schedule and protocol

Exclusion Criteria:

• Pre-menarche or post-menopause
• Diagnosis of Type 1 or Type 2 Diabetes Mellitus
• Severe renal dysfunction (creatinine >1.4 mg/dL or eGFR below 45 mL/minute/1.73 m2
• History of lactic acidosis or diabetic ketoacidosis
• ALT or AST > 2.5 times the upper limit of normal
• Significant mental or chronic systemic illness that might confound pain assessment or the inability to complete the study
• Current/planning pregnancy or breastfeeding
• Inability to read English

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: Placebo; Placebo tablets orally daily for a total of 6 months of treatment.	Drug: Placebo; 1 tablet orally with evening meal for 2 weeks, then 1 tablet twice daily for 2 weeks, then 3 tablets split twice daily for 2 weeks, then 4 tablets split twice daily, for a total of 6 months of treatment.; Other Names: Placebo capsule
Experimental: Metformin; metformin hydrochloride 500 mg capsules daily for a total of 6 months of treatment	Drug: Metformin Hydrochloride; Metformin dosage titrated from 500 mg/daily for 2 weeks, then 1000 mg/daily for 2 weeks, 1500 mg/daily for 2 weeks, and then achieving 2000 mg/daily for a duration of 6 months of treatment.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in pain assessed by the Brief Pain Inventory Interference Scale (BPI) over 6 months	The BPI Interference Scale is a 7-item composite pain measurement. This self-report measure assesses the extent to which pain interferes with various components of physical and emotional functioning and sleep. The items in this scale can be grouped into those that assess physical functioning (general activity; walking ability; normal work, including both work outside the home and housework), those that assess emotional functioning (mood; relations with people; enjoyment of life), and a single item that assess the extent to which pain interferes with sleep. The arithmetic mean of the seven interference items can be used as a measure of pain interference. The BPI is anchored between a scale of zero (no pain/interference) to ten (maximum pain/interference). The magnitude of treatment-associated change in BPI Interference Scale scores in open-label and randomized clinical trials ranges from 1 to 3 points, depending on the specific pain conditions and treatments studied.	once at each of the three visits (at baseline, 3 months, 6 months)
Change in pain severity measured by Visual Analog Scale (VAS) over 6 months	VAS: A measurement of pain intensity, assessed by a 0 to 10 numerical rating scale, to rate maximum and average pain intensity over the preceding 7 days. Higher scores indicate more severe pain intensity.	once at each of the three visits (at baseline, 3 months, 6 months)
Change in emotional functioning assessed by Beck Depression Inventory-II (BDI) over 6 months	The BDI is a 21-item self-report instrument that provides a rapid assessment of depressive symptoms. BDI has been used in many studies of chronic pain, including chronic pelvic pain and endometriosis. Total scores on the BDI range from 0 to 63. The BDI takes about 5-10 minutes to complete. Scores below 13 should be considered to reflect "minimal or no" depression, with score ranges of 14 to 19, 20 to 28, and 29 to 63 reflect "mild to moderate," "moderate to severe," and "severe" depression, respectively.	once at each of the three visits (at baseline, 3 months, 6 months)
Change in ratings of overall improvement assessed by the Patient Global Impression of Change scale (PGIC)	The PGIC is a seven-point single-item scale with options ranging from 'very much worse' to 'very much improved'. There has been widespread use of the PGIC in recent endometriosis clinical trials, as it readily interprets a person's evaluation of the importance of their improvement or worsening.	once at each of the three visits (at baseline, 3 months, 6 months)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in quality of life, measured via Endometriosis Health Profile-30 (EHP-30)	The EHP-30 is a reliable instrument and recommended by the American Society for Reproductive Medicine and the European Society for Human Reproduction and Embryology. The questionnaire includes 30 questions in five subcategories, with each category addressing specific problem areas of pain, control and powerlessness, emotional wellbeing, social support, and self-image.	once at each of the three visits (at baseline, 3 months, 6 months)
Changes in sexual satisfaction for participants who are sexually active measured by the New Sexual Satisfaction Scale	The NSSS is a 20-item measure assessing sexual sensations, sexual presence/awareness, sexual exchange, emotional connection/closeness, and sexual activity. The full scale takes 5 minutes to complete.	once at each of the three visits (at baseline, 3 months, 6 months)
Complete health and medication history assessed by the World Endometriosis Research Foundation (WERF) questionnaire	Study participants will complete an expanded version of the WERF questionnaire for a complete health and medication history	once at each of the three visits (at baseline, 3 months, 6 months)
Changes in serum angiogenic/inflammatory markers	Serum samples will also be obtained for measures of inflammation, to test the hypothesis that endometriosis-relevant inflammatory markers will decrease over time in patients treated with metformin compared to those receiving placebo. These markers will include IL-6, IL-8, and VEGF based on the results of prior studies in which metformin appeared to reduce these levels in humans with endometriosis and from endometriotic implants in rats. C-reactive protein (CRP) will also be assessed; CRP has been shown to be upregulated, especially when examined with a high sensitivity assay making it possible to detect subclinical inflammation in women with endometriosis.	once at each of the three visits (at baseline, 3 months, 6 months)

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in school and/or work attendance	School and/or work attendance will be assessed at each visit.	once at each of the three visits (at baseline, 3 months, 6 months)
Change in pregnancy status	Urine pregnancy test throughout the study as current pregnancy is an exclusion criteria	once at each of the three visits (at baseline, 3 months, 6 months)
Changes in serum lactate levels	Serum lactate will be measured at baseline and then possibly at three and six months, if needed.	baseline, three and six months if needed
Changes in pain	Subjects will keep a daily symptom diary to track pain for 6 months.	daily for 6 months
Incidence of vaginal bleeding over six months	Measurement of the incidence of vaginal bleeding using a daily symptom diary to document the presence/absence of vaginal bleeding	daily for 6 months
Usage of any pain medications (both prescription and over the counter)	Usage of any pain medications (both prescription and over the counter) tracked in a daily symptom diary for 6 months	daily for 6 months
Changes in height	Height, in cm, will be obtained at each study visit (at baseline, 3 months, and 6 months).	once at each of the three visits (at baseline, 3 months, 6 months)
Changes in weight	Study subjects will have their weight obtained at each study visit given the potential impact on weight by metformin.	once at each of the three visits (at baseline, 3 months, 6 months)
Changes in serum insulin c-peptide level	Serum insulin c-peptide levels will be collected at baseline and again at 6-months given metformin impact on lowering c-peptide levels.	at baseline and 6 months
Changes in hemoglobin and mean corpuscular volume	A Complete Blood Count (CBC) will be collected at baseline and again at 6-months due to the potential adverse effect of megaloblastic anemia by metformin, which would be detected by the hemoglobin and mean corpuscular volume.	at baseline and 6 months
Changes in vitamin B12 levels	Serum vitamin B12 levels will be obtained at baseline and at 6 months due to the possible adverse effect of vitamin b12 deficiency by metformin	at baseline and 6 months
Changes in lipid levels	A lipid panel will be collected at baseline and again at 6-months due to the potential lipid-lowering activity of metformin.	at baseline and 6 months
Changes in hemoglobin A1c	At each study visit, (baseline, 3 months, and 6 months), HbA1c will be assessed serially given the glycemic impact and effect of reducing HbA1c by metformin.	once at each of the three visits (at baseline, 3 months, 6 months)
Changes in metabolic panel	At each study visit, (baseline, 3 months, and 6 months), a comprehensive metabolic panel will be assessed serially to monitor for any potential kidney impairment that might affect continuation of treatment or changes in electrolytes in the setting of gastrointestinal distress.	once at each of the three visits (at baseline, 3 months, 6 months)
Changes in temperature	A physical exam will be conducted at baseline, three months, and six months to obtain changes in temperature.	once at each of the three visits (at baseline, 3 months, 6 months)
Changes in heart rate	A physical exam will be conducted at baseline, three months, and six months to obtain changes in heart rate.	once at each of the three visits (at baseline, 3 months, 6 months)
Changes in blood pressure	A physical exam will be conducted at baseline, three months, and six months to obtain changes in blood pressure.	once at each of the three visits (at baseline, 3 months, 6 months)

Collaborators and Investigators

• Sponsor: Boston Children's Hospital
• Investigators: Principal Investigator: Jessica Shim, MD, Boston Children's Hospital

Publications and helpful links

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Study record dates

Study Major Dates

• Study Start (Actual): May 22, 2025
• Primary Completion (Estimated): January 1, 2027
• Study Completion (Estimated): January 1, 2027

Study Registration Dates

• First Submitted: September 10, 2024
• First Submitted That Met QC Criteria: September 20, 2024
• First Posted (Actual): September 25, 2024

Study Record Updates

• Last Update Posted (Actual): February 20, 2026
• Last Update Submitted That Met QC Criteria: February 18, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Pain; Chronic pain; Metformin; Pelvic pain; Endometriosis; Physiological Effects of Drugs; Female Urogenital Diseases; Genital Diseases, Female
• Additional Relevant MeSH Terms: Urogenital Diseases; Genital Diseases; Neurologic Manifestations; Female Urogenital Diseases and Pregnancy Complications; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Pain; Chronic Pain; Endometriosis; Pelvic Pain; Genital Diseases, Female; Female Urogenital Diseases; Organic Chemicals; Biguanides; Guanidines; Amidines; Metformin
• Other Study ID Numbers: IRB-P00049391

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: IPD will not be shared so that patient privacy and confidentiality is maintained during this study.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes