Metformin Effects on Metabolic, Vitamin B12, Iron, Erythropoietin, and Hematological Parameters in Women With PCOS (MET-PCOS)

Polycystic ovary syndrome (PCOS) is a common and heterogeneous endocrine and metabolic disorder characterized by reproductive, endocrine, and metabolic abnormalities. Insulin resistance, hyperinsulinemia, dyslipidemia, excess weight, and disturbances in reproductive function are important components of the PCOS phenotype. Metformin is an insulin-sensitizing medication widely used to address metabolic abnormalities associated with PCOS.

This double-blind, placebo-controlled, parallel-group randomized controlled trial was designed to evaluate longitudinal changes in metabolic, vitamin B12, iron-status, erythropoietic, and hematological parameters among women with PCOS during six months of metformin therapy. The study also examined selected associations among demographic, clinical, reproductive, familial, metabolic, vitamin B12, iron-status, erythropoietic, and hematological characteristics.

Women aged 18-40 years with PCOS confirmed by a specialist in Obstetrics and Gynecology were eligible for participation. Participants were excluded if they had chronic hemolytic anemia, chronic kidney disease, endocrine disorders other than PCOS, hepatic disorders, metabolic disorders, cardiovascular disease, or other concurrent medical conditions that could influence glucose metabolism, iron status, vitamin B12, erythropoietin, or hematological parameters. Women who had received insulin-sensitizing agents, iron supplementation, hormonal therapy, vitamin B12 supplementation, or other medications known to substantially affect the study outcomes during the predefined period before enrollment were also excluded.

Following baseline assessment, eligible participants were randomly allocated in a 1:1 ratio using a computer-generated random allocation sequence to either the metformin intervention group or the matching placebo group. Participants in the intervention group received metformin at a total daily dose of 1500 mg, administered in three divided doses with meals. Participants in the control group received a corresponding matching placebo according to the same administration schedule. Both groups continued to receive routine clinical care.

The double-blind design was maintained throughout the study. Participants were blinded to treatment allocation, and investigators involved in participant assessment and outcome evaluation were also blinded to treatment assignment. Matching preparations were used to minimize the possibility of identifying treatment allocation based on appearance.

Clinical, anthropometric, biochemical, iron-status, vitamin B12, erythropoietic, and hematological assessments were performed at three predefined time points: baseline, 3 months, and 6 months. Metabolic assessments included body mass index, fasting blood glucose, serum insulin, HOMA-IR, total cholesterol, triglycerides, LDL-C, and HDL-C. Iron-status assessments included serum iron, total iron-binding capacity, ferritin, and transferrin saturation. Serum vitamin B12 and erythropoietin were also assessed. Hematological assessments included hemoglobin, hematocrit, red blood cell count, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, red cell distribution width, white blood cell count, lymphocytes, neutrophils, eosinophils, basophils, monocytes, and platelet count.

The study was conducted in obstetrics and gynecology clinics affiliated with the Ministry of Health in Jordan. The study period extended from August 2025 to February 2026. A total of 400 women were initially enrolled and randomly allocated, with 200 participants assigned to each treatment group. During the six-month follow-up period, 100 participants did not complete the required assessments, leaving 300 participants in the final longitudinal analysis, comprising 150 participants in the metformin group and 150 participants in the matching placebo group.

No additional structured educational, behavioral, lifestyle, or self-management intervention was introduced as part of the study protocol. Participants continued to receive routine clinical care. Lifestyle behaviors, including physical activity, dietary intake, and adherence to lifestyle recommendations, were not systematically quantified using validated assessment instruments.

Longitudinal changes across baseline, 3 months, and 6 months were evaluated using repeated-measures analysis of variance. Associations between selected continuous variables were examined using Pearson's correlation coefficient when appropriate, while Spearman's rank-order correlation coefficient was used for ordinal variables or variables that did not meet the assumptions required for Pearson correlation. Correlation analyses were considered exploratory and hypothesis-generating because multiple associations were examined.

The study received ethical approval from the Ethical Board of the Jordanian Ministry of Health, Amman, Jordan (Approval No. 99923), and the Institutional Review Board of Al-Ahliyya Amman University (Approval No. 2026-2025/30/1). Written informed consent was obtained from all participants before enrollment. The study was conducted in accordance with the ethical principles of the Declaration of Helsinki.