The Relationship of the Intestinal Microbiome and the Menstrual Cycle
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ClinicalTrials.gov Identifier: NCT03581201 |
Recruitment Status : Unknown
Verified August 2019 by Alexandra Kautzky-Willer, Medical University of Vienna.
Recruitment status was: Recruiting
First Posted : July 10, 2018
Last Update Posted : September 3, 2019
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Condition or disease | Intervention/treatment |
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Sex Hormones Microbial Colonization | Diagnostic Test: Laboratory measurements Diagnostic Test: Stool samples Diagnostic Test: Bioimpedance analysis |
Our gut has a complex and diverse bacterial population which is called the microbiome. The number of bacteria in the intestine is estimated to exceed 10^14. The composition of the microbiome is individual and changes over the lifetime of the host.
The composition of a healthy microbiome consists more than 90% of bacteria from the Bacteroidetes and Firmicutes phyla types. Nevertheless the microbiome varies even between healthy individuals and evolves over the lifetime.
Most of the microorganisms are not pathogen, thus they have been shown to interact with several physiological processes in our body. In Addition it has been shown that the bacterial population has an impact on building our gut epithelial cells, our immunology and the defence against pathogens.
Interestingly estrogen and the microbiome seem to be under reciprocal influence. In our body estrogen is only active in the deconjugated form. Therefore, after it was conjugated in the liver, the bacteria in the gut can perform a deconjugation through the secretion of the enzyme ß-glucuronidase. Ultimately, the activated estrogen is going back into blood circulation, otherwise it would leave the body through bile excretion. The composition of the microbiome is fundamental, because the presence and abundance of different gene expressions varies between the different types of bacteria. The bacterial genes which are responsible for metabolizing estrogens are called the estrobolome. However, data whether there is a relationship of the changes of the sex hormones during the menstrual cycle and the intestinal microbiome in women is sparse.
Parts of the estrogens circulating in the body are metabolised in the liver and are then secreted to the intestine conjugated with glucuronide. The intestinal microbiota could potentially affect estrogen metabolism via Beta-glucuronidase activity. Beta-glucuronidase is an enzyme that catalyses the deconjugation of estrogen. As a consequence, it may bind to estrogen receptors and unfold its downstream effects.
Study Type : | Observational |
Estimated Enrollment : | 20 participants |
Observational Model: | Cohort |
Time Perspective: | Prospective |
Official Title: | The Relationship of the Intestinal Microbiome and the Dynamic Changes of Sex Hormone Concentrations in Women at Childbearing Age |
Actual Study Start Date : | July 18, 2018 |
Estimated Primary Completion Date : | June 13, 2020 |
Estimated Study Completion Date : | July 1, 2020 |

Group/Cohort | Intervention/treatment |
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Oral contraception
Healthy females at childbearing age with oral contraception.
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Diagnostic Test: Laboratory measurements
Laboratory measurements will be collected every week during the Duration of one menstrual cycle and includes the following:
Diagnostic Test: Stool samples For a Duration of one menstrual cycle the study participants will be instructed to collect stool samples every two days. The investigation of the intestinal microbiome will be done by sequencing the 16S rRNA gene. Diagnostic Test: Bioimpedance analysis The Bioimpedance analysis (BIA) is used for the measurement of body composition and will be done at every study visit. |
No contraception
Healthy females without any contraception at all.
|
Diagnostic Test: Laboratory measurements
Laboratory measurements will be collected every week during the Duration of one menstrual cycle and includes the following:
Diagnostic Test: Stool samples For a Duration of one menstrual cycle the study participants will be instructed to collect stool samples every two days. The investigation of the intestinal microbiome will be done by sequencing the 16S rRNA gene. Diagnostic Test: Bioimpedance analysis The Bioimpedance analysis (BIA) is used for the measurement of body composition and will be done at every study visit. |
- Changes of the B-Glucuronidase, expressed by the intestinal microbiome, during the menstrual cycle in women at childbearing age [ Time Frame: Up to 7 weeks ]
Parts of the estrogens circulating in the body are metabolised in the liver and are then secreted to the intestine conjugated with glucuronide. The intestinal microbiota could potentially affect estrogen metabolism via β-glucuronidase activity. β-glucuronidase is an enzyme that catalyses the deconjugation of estrogen. As a consequence, it may bind to estrogen receptors and unfold its downstream effects.
RNA and total DNA will be extracted from the fecal samples and microbiome community composition will be assessed by sequencing the 16s ribosomal RNA gene. Then reverse transcription of the total RNA and targeted amplification and sequencing of β-glucuronidase gene fragment will be applied in order to find out which bacteria are producing the β-glucuronidase enzyme.
Furthermore, the enzymatic activity in the samples will be measured using the β-glucuronidase colorimetric assay with p-nitrophenol glucuronide.
- Changes of the Beta-Glucuronidase during the menstrual cycle in women with oral contraception [ Time Frame: Up to 7 weeks ]
- Changes of the Beta-Glucuronidase during the menstrual cycle in women without any contraception [ Time Frame: Up to 7 weeks ]
- Changes of the intestinal microbiome during the menstrual cycle in women at childbearing age with- and without contraception [ Time Frame: Up to 7 weeks ]
- Relationship of the β-Glucuronidase with the changes of the female sex hormones during the menstrual cycle in women at childbearing age. [ Time Frame: Up to 7 weeks ]
- Relationship of the intestinal microbiome with the changes of the female sex hormones during the menstrual cycle in women at childbearing age. [ Time Frame: Up to 7 weeks ]

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Ages Eligible for Study: | 18 Years to 40 Years (Adult) |
Sexes Eligible for Study: | Female |
Gender Based Eligibility: | Yes |
Accepts Healthy Volunteers: | Yes |
Sampling Method: | Probability Sample |
Inclusion Criteria:
- women at childbearing age
- age 18-40 years
- BMI 18.5-24.9 kg/m²
- taking oral contraceptives
- not having any contraceptives
Exclusion Criteria:
- chronic and acute infectious diseases
- history of taking antibiotics or probiotics in the last 3 months
- gastrointestinal disorders in the last 3 months
- Polycystic Ovary Syndrome
- disorders of the menstrual cycle (e.g. oligomenorrhea, anovulation)
- other than mediterranean diet

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT03581201
Contact: Alexandra Kautzky-Willer, Prof. Dr. | +434040021260 | alexandra.kautzky-willer@meduniwien.ac.at | |
Contact: Michael Leutner, Dr.med.univ., PhD, MSc | michael.leutner@meduniwien.ac.at |
Austria | |
Medical University of Vienna | Recruiting |
Vienna, Austria, 1090 | |
Contact: Alexandra Kautzky-Willer, Univ.Prof.Dr. +434040021260 alexandra.kautzky-willer@meduniwien.ac.at |
Principal Investigator: | Alexandra Kautzky-Willer, Prof. Dr. | Department of Internal Medicine III, Clinical Division of Endocrinology and Metabolism, Unit of Gender Medicine, Medical University of Vienna |
Responsible Party: | Alexandra Kautzky-Willer, Univ. Prof. Dr., Head of the Gender Medicine Unit, Medical University of Vienna |
ClinicalTrials.gov Identifier: | NCT03581201 |
Other Study ID Numbers: |
MB2018 |
First Posted: | July 10, 2018 Key Record Dates |
Last Update Posted: | September 3, 2019 |
Last Verified: | August 2019 |
Studies a U.S. FDA-regulated Drug Product: | No |
Studies a U.S. FDA-regulated Device Product: | No |
intestinal microbiome oral contraceptives estrogens bacterial population |
hormone status glucose profiles lipid parameters body composition |
Communicable Diseases Infections Disease Attributes Pathologic Processes |