PCOS: planned trial to test Lactobacillus crispatus with metformin, with no results available yet

Three groups to assess the potential benefit of the combination

The trial plans to include 135 women aged 18 to 40 with PCOS diagnosed according to the Rotterdam criteria. Conducted at the All India Institute of Medical Sciences in Bhubaneswar, it will randomly assign participants to three groups: a probiotic containing Lactobacillus crispatus, metformin alone or their combination.

The intervention is planned to last 12 weeks. The primary outcome is the change in HOMA-IR, an indicator of insulin resistance. The researchers also plan to measure blood and faecal calprotectin, acylated ghrelin, total testosterone and faecal microbiota composition, among other parameters.

According to the abstract, 26 participants had been recruited as of 30 August 2026, out of the planned 135. The study is scheduled to end in June 2027, with publication of the results targeted for mid-to-late 2027. This timeline remains provisional.

A gut-related hypothesis, not a demonstrated mechanism

The authors’ rationale rests on possible links between gut microbiota imbalance, inflammation and insulin resistance in PCOS. They propose that a probiotic containing Lactobacillus crispatus could have an effect that complements that of metformin.

This explanation is a biological hypothesis. The protocol does not show that the probiotic restores the intestinal barrier, reduces inflammation or improves reproductive health. The ambitious wording in the abstract describes the researchers’ objectives, not effects already observed.

What this trial could clarify

Comparing the combination with metformin alone could help determine whether the probiotic provides an additional benefit on the parameters measured. The group receiving only the probiotic will allow another comparison, but no placebo group is described.

The trial is open-label: participants and study teams know which treatment has been assigned. This feature may influence behaviour and some outcomes. Moreover, a possible improvement in HOMA-IR over 12 weeks would not be enough to establish a lasting benefit for metabolic complications or fertility.

When deciding what to buy or which treatment to use, the distinction is clear: this protocol alone does not justify adding a probiotic to metformin or replacing metformin with one.

What we can take away

This trial asks a relevant question about Lactobacillus crispatus in PCOS. Its results will be needed to determine whether combining it with metformin provides a measurable benefit.