Teens with "unhealthy" gut bacteria may face a higher risk of obesity and polycystic ovary syndrome (PCOS), according to a study which may lead to earlier diagnosis of the chronic diseases.

PCOS, a hormone disorder characterised by high levels of the male hormone testosterone in women's blood, can cause acne, excess hair growth, and irregular periods, and affects 6-18 per cent of women of reproductive age globally, the study, published in the Journal of Clinical Endocrinology & Metabolism, noted.

Women and teen girls with PCOS may also experience side effects beyond infertility and menstrual irregularities, like psychological issues including anxiety and depression that continue well beyond fertile age, the study said.

"We found that in adolescents with PCOS and obesity, the bacterial profile (microbiome) from stool has more 'unhealthy' bacteria compared to teens without PCOS," said Melanie Cree Green, the study's co-author from Children's Hospital Colorado in the US.

"The unhealthy bacteria is related to higher testosterone concentrations, and markers of metabolic complications," Green added.

Analysing the stool samples of 58 teens with obesity, the scientists found that the community of thousands of bacterial species living in the guts of girls with PCOS are altered compared to those in teens without the condition.

According to the scientists, these girls had more "unhealthy" bacteria in their stool samples which was related to higher testosterone levels, and other markers of metabolic syndrome like higher blood pressure, liver inflammation, and elevated levels of the fat molecules triglycerides.

"The gut microbiome may play a role in PCOS and its related metabolic complications, and these changes can be found in teenagers who are early in the course of the condition," Green said.