Can oral contraceptive therapy improve the vaginal microbiome in women with PCOS?

By Dr. Chinta SidharthanDec 7 2023Reviewed by Lily Ramsey, LLM

In a recent study published in the journal BMC Medicine, researchers from China examined a longitudinal cohort of women undergoing oral contraceptive therapy for polycystic ovary syndrome (PCOS) to understand the impact of the contraceptive medication-induced change in hormonal levels on the vaginal microbiome.

Study: Change of the vaginal microbiome with oral contraceptive therapy in women with polycystic ovary syndrome: a 6-month longitudinal cohort study. Image Credit: Alena Menshikova/Shutterstock.com

Background

Polycystic ovary syndrome, or PCOS, is a condition that affects about 10% of women of reproductive age, with major symptoms being abnormal menstruation or oligomenorrhea and hyperandrogenism, along with acne and obesity.

Although the etiology of PCOS remains unclear, recent studies have hypothesized an association between PCOS and the vaginal microbiome.

The vaginal microbiota is believed to have a direct association with female hormone levels and has been considered a potential biomarker for PCOS.

Various studies have reported the dominance of Lactobacillus in the vaginal microbiome of a healthy female and an increased abundance of Mycoplasma hominis, Gardnerella vaginalis, and Prevotella in the vaginal microbiome of women with PCOS.

A negative correlation has also been observed between the abundance of vaginal Streptococcus and the levels of follicle-stimulating hormone.

However, the current evidence for the association between PCOS and the vaginal microbiome comes only from retrospective studies. Furthermore, the treatment methods for PCOS are focused largely on managing the condition through lifestyle changes and oral contraceptives to regulate the menstruation cycles.

The impact of oral contraceptives on normalizing hormone levels and, subsequently, on the vaginal microbiome remains unclear.

About the study

In the present study, the researchers conducted a longitudinal analysis of a cohort of PCOS patients who were being treated with oral contraceptives for six months to understand whether the change in hormone levels brought about by oral contraceptives has an impact on the vaginal microbiome.

They hypothesized that the oral contraceptives would improve the hormonal balance and subsequently result in a healthier vaginal microbiome.

Women diagnosed with PCOS between 2019 and 2020 were included in the study if they had at least two of the three symptoms consisting of biochemical or clinical indications of hyperandrogenism, anovulation or oligovulation, or testosterone levels of greater than 1.77 nmol per liter, along with the presence of polycystic ovaries.

The study only included patients who were being treated with oral contraceptives and lifestyle coaching. Vaginal swab samples were obtained at baseline and three and six months.

Demographic information such as age, education level, and marital status were obtained through questionnaires. In contrast, biometric measurements such as waist and hip circumferences, weight, and height were obtained to calculate the waist-to-hip ratio and body mass index.

The vaginal swabs were processed for deoxyribonucleic acid (DNA) extraction and amplification of the 16S ribosomal ribonucleic acid (rRNA) region.

Additionally, venous blood samples were collected, and chemiluminescent immunoassays were used to assess the levels of luteinizing hormone, follicle-stimulating hormone, estradiol, anti-Mullerian hormone, and total testosterone.

The amplified 16S rRNA sequences were clustered based on similarity to operational taxonomic units, which were then used to calculate alpha-diversity indices such as the Simpson and Shannon indices.

The potential associations between the diversity within the vaginal microbiome and various hormone indicators were then examined while adjusting for confounding demographic and biometric factors.

Results

The results suggested that further research is required to understand whether hormone level changes are associated with the diversity within the vaginal microbiome.

The overall findings showed that the vaginal microecology in some of the participants improved over time, with the average abundance of Lactobacillus increasing over time.

The latent class trajectory modeling analysis on hormone levels and the relative abundance of Lactobacillus revealed five different patterns.

While the Lactobacillus abundance was found to increase with oral contraceptive treatment in some patients, in others, no such change was observed, and the baseline levels of testosterone were thought to play a role.

While no significant associations were observed between changes in the vaginal environment and female hormone levels in patients with PCOS, other studies have reported longitudinal changes in the relative abundances of Gardnerella vaginalis, Lactobacillus, and anaerobic taxa such as Mobiluncus and Bacteroides in association with different stages of the menstrual cycle, as well as menopause.

These findings, combined with observations of an increase in Lactobacillus abundance after hormone replacement therapy in menopausal women, indicated that the vaginal microbiome is linked to female hormone levels, and further research is required to understand these associations in women with PCOS.

Conclusions

Overall, the findings indicated that oral contraceptive therapy improved the abundance of Lactobacillus in some PCOS patients. Still, hormone levels were not found to be significantly associated with longitudinal changes in the vaginal microbiome.

However, associations between vaginal microbiome diversity and changing hormonal levels linked to the menstrual cycle and menopause indicated that further research is warranted to understand these associations in women with PCOS.