NEW YORK - Teenagers who have irregular periods are more likely to be overweight and obese and to have early warning signs of diabetes and heart disease than those with regular menstrual cycles, a study said.

While the link between irregular periods and heart disease and diabetes is well-established in older women, the findings, published in "Fertility and Sterility," suggest that doctors might be able to identify this risk much earlier - and try to do something about it.

"There may be a misconception in adolescent medicine ...that it 'takes a couple of years after menarche to get the engine running' and hence one might not want to be concerned about irregular adolescent menstrual cycles until much later," said Charles Glueck, one of the study's authors, from the Cholesterol and Metabolism Center at the Jewish Hospital of Cincinnati.

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"That's clearly wrong," he added, noting that even in young teenagers, very irregular menstrual cycles are not normal and should not be ignored.

Glueck and his colleagues followed 370 girls, starting at age 14, as part of a larger study initiated by the National Heart, Lung and Blood Institute.

Once every year, girls were asked how long it had been since their last menstrual cycle. Researchers also periodically measured their levels of different sex hormones, glucose and insulin, and blood pressure.

They also collected information on girls' height, weight and waist circumference.

The authors defined irregular menstrual cycles as lasting more than 42 days, a criterion that's meant to catch the 2 percent of girls with the least regular periods, Glueck said.

Between age 14 and 19, 269 of the girls reported regular periods at every annual visit. Another 74 of them had only one report of an irregular period, 19 girls had two reports, and eight said it had been at least 42 days since their last period at three or more visits.

The girls with the most reports of irregular periods were already heavier than others at age 14, and gained more weight and inches on their waist during the study. They also had higher levels of testosterone.

By age 25, those who hadn't reported an irregular period an average body mass index (BMI), a measure of weight against height, of 26.8. Those who had reported irregular periods at three or more appointments had an average BMI of 37.8 while girls who reported one or two irregular periods had BMIs somewhere in the middle.

Reports of irregular periods were also linked to higher levels of blood sugar and insulin at age 25.

The authors couldn't be sure what was happening with girls' menstrual cycles during the rest of the year. Also, the findings do not prove that irregular periods cause girls to gain weight or are responsible for the increases in glucose and insulin levels -- rather, the irregularity could signal another problem.

One possibility is that the ovaries might respond to changes in metabolism, such as increased insulin levels, said Alice Chang, an endocrinologist at UT Southwestern Medical center, suggesting that some of the diabetes-related risks came before problems with ovulation.

Irregular periods might be a sign of polycystic ovary syndrome, or PCOS, which can cause fertility problems, Glueck said. But catching it in adolescence means it can be "very successfully treated."

Chang, who was not involved in the latest study, agreed that the implications for PCOS are an important message to take from the study.

"When I see women diagnosed with PCOS, they often have symptoms all through adolescence, but it's not put together for them. We need to be more aggressive in adolescents about treating PCOS and treating obesity," she said.