Obstetrics & Gynecology · Medical Literature
Effects of combined metformin and cabergoline versus metformin alone on inflammatory markers in Iraqi patients with PCOS and hyperprolactinemia: a randomized clinical trial.
Abstract
Polycystic ovarian syndrome (PCOS) is by far the most prevalent metabolic disease affecting women during their reproductive life. Obesity is a frequently associated manifestation of polycystic ovary syndrome. Central body fat accumulation has been associated with the production of a variety of cytokines associated with low-grade inflammation in polycystic ovary syndrome. This study aimed to evaluate the effect of metformin and cabergoline, each alone and in combination, on several immune markers in women with hyperprolactinemia. The three-arm interventional study included 75 women with PCOS according to the Rotterdam criteria. They were categorized into three groups: those given metformin alone, those given cabergoline alone, and those given combined agents. Baseline and follow-up characteristics included immune markers such as anti-glutamic acid decarboxylase (anti-GAD) antibodies, gonadotropin-releasing hormone (GnRH) antibodies, and interleukin-18 (IL-18). It was observed that the use of either drug alone resulted in no significant change in the level of anti-GAD; however, combined use of the two drugs resulted in a significant reduction in the level, indicating that these two drugs acted synergistically. It was observed that the combined use of either drug resulted in a more significant reduction of GnRH antibody level. It was observed that the combined use of either drug resulted in a more significant reduction of IL-18 level (P <0.001). Metformin and cabergoline are efficient, act synergistically, and are safe when used in combination, reducing IL-8 levels and autoantibodies to GAD and GnRH in women with PCOS.
Clinical relevance
PCOS is the most prevalent metabolic-reproductive disorder in women of reproductive age, and the co-existence of hyperprolactinemia—present in approximately 30% of PCOS cases—compounds endocrine dysfunction by further disrupting the hypothalamic-pituitary-ovarian axis. Low-grade chronic inflammation, evidenced by elevated cytokines and circulating autoantibodies (anti-GAD, anti-GnRH) and interleukins, is increasingly recognized as a driver of PCOS pathophysiology, yet no established pharmacologic strategy specifically targets this immunoinflammatory burden in the PCOS-hyperprolactinemia phenotype. This trial is among the first to evaluate the immunomodulatory synergy of combining metformin (an insulin sensitizer) with cabergoline (a dopamine D2 agonist) in this dual-diagnosis population, directly addressing a clinically relevant therapeutic gap.
Key findings
1. Three-arm design: 75 women with PCOS (Rotterdam criteria) and hyperprolactinemia were randomized into three equal groups (n=25 each): metformin alone (500 mg twice daily), cabergoline alone (0.5 mg once weekly), and combination therapy, assessed at baseline and at 90-day follow-up. 2. Anti-GAD antibodies: Neither metformin monotherapy nor cabergoline monotherapy produced a statistically significant reduction in anti-GAD antibody levels; only the combination arm achieved a significant reduction, indicating a true pharmacodynamic synergism between the two agents. 3. Anti-GnRH antibodies: Combined metformin plus cabergoline produced a more significant reduction in circulating anti-GnRH antibody levels compared to either agent used alone, further supporting a synergistic immunomodulatory mechanism. 4. IL-18 (interleukin-18): The combination arm produced a statistically significant reduction in IL-18 levels (p < 0.001), a pro-inflammatory cytokine implicated in insulin resistance and low-grade inflammation in PCOS, compared to monotherapy arms. 5. Safety profile: The combination of metformin and cabergoline was reported to be safe and well-tolerated in this population across the 90-day treatment period, with no reported serious adverse events noted in the abstract. 6. Note on quantitative precision: The abstract does not report exact pre/post mean values, confidence intervals, effect sizes, or NNT/NNH for the immunologic endpoints; findings are limited to directional significance and p-values as reported above.
Practice implications
In women of reproductive age presenting with PCOS confirmed by Rotterdam criteria who also carry a diagnosis of hyperprolactinemia, clinicians should consider combination therapy with metformin (500 mg twice daily) and cabergoline (0.5 mg once weekly) over either agent alone when immunoinflammatory burden—reflected by elevated IL-18, anti-GAD, or anti-GnRH antibodies—is a concern, as monotherapy with either drug appears insufficient to meaningfully suppress these markers. This combination should be evaluated at a minimum 90-day interval to assess immunologic response alongside standard hormonal and metabolic parameters. Given the limited sample size (n=75) and single-center Iraqi cohort, these findings should currently inform hypothesis generation and patient-level shared decision-making rather than serve as a standalone basis for guideline change; replication in larger, multicenter, placebo-controlled trials with full reporting of effect sizes and confidence intervals is needed before broad adoption.