TUESDAY, Aug. 24 (HealthDay News) -- Nicotine may directly promote the development of breast cancer by binding to a certain cell receptor, says a new study.

Many chemicals in tobacco are believed to be carcinogens but little is known about how nicotine might contribute to cancer cell growth. What is known is that when nicotine binds to the nicotinic acetylcholine receptor (nAChR), it promotes smoking addiction.

In this study, Taiwanese researchers analyzed 276 breast tumor samples to determine whether subunits of nAChR were overproduced in breast cancer cells compared with surrounding normal cells.

The researchers found that breast cancer cells consistently overproduced the alpha 9 subunit of nAChR (a9-nAChR) and that production of this subunit was higher in advanced-stage breast cancer than in early-stage cancer. They then conducted laboratory tests that showed reducing levels of a9-nAChR inhibited tumor growth, while increasing levels of the subunit or treating more normal breast cells with nicotine led to the development of cancer characteristics.

"These results imply that receptor-mediated carcinogenic signals play a decisive role in biological functions related to human breast cancer development," concluded Yuan-Soon Ho, of the Taipei Medical University, and colleagues in a news release from the Journal of the National Cancer Institute, which published the study online Aug. 23.

More information

The American Cancer Society has more about the causes of breast cancer  .

FRIDAY, Aug. 27 (HealthDay News) -- A new study finds that mothers who don't breast-feed their children are at greater risk of developing type 2 diabetes later in life compared to those who do breast-feed.

Type 2 diabetes occurs when the body's cells gradually lose their sensitivity to insulin; the illness is often linked to obesity.

Researchers from the University of Pittsburgh studied more than 2,200 women aged 40 to 78. They found that 27 percent of mothers who didn't breast-feed developed type 2 diabetes, almost double the rate among women who breast-fed or never gave birth.

The researchers say the differences between the groups held up even after they adjusted the statistics for factors such as age, race, levels of physical activity and body-mass index.

"Diet and exercise are widely known to impact the risk of type 2 diabetes, but few people realize that breast-feeding also reduces mothers' risk of developing the disease later in life by decreasing maternal belly fat," said Dr. Eleanor Bimla Schwarz, an assistant professor of medicine, epidemiology, and obstetrics, gynecology and reproductive sciences at the University of Pittsburgh, in a news release from the university.

"Our study provides another good reason to encourage women to breast-feed their infants, at least for the infant's first month of life," Schwarz said. "Clinicians need to consider women's pregnancy and lactation history when advising women about their risk for developing type 2 diabetes."

The study, which was funded by the U.S. National Institute of Diabetes and Digestive and Kidney Diseases and the National Institute of Child Health and Development, appears in the September issue of the American Journal of Medicine.

More information

There's more on breast-feeding at the U.S. National Library of Medicine.

THURSDAY, Aug. 19 (HealthDay News) -- Birth control pills are equally effective in obese and thinner women, claims a study that challenges the belief that oral contraceptives may not reliably prevent pregnancy in heavier women.

The study included 226 women, aged 18 to 35, who were normal weight or overweight. They were randomly assigned to take either a lower- or higher-dose version of a birth control pill.

After three or four months of using the pill (the time it takes for a woman's body to get used to the contraceptive), the women were checked to see if the pill was suppressing ovulation.

Of the 150 women who used the pill consistently, ovulation occurred in three of the 96 normal-weight women and in one of the 54 obese women. Women who were not consistent about taking the pill were more likely to ovulate, said the researchers at the New York-Presbyterian Hospital/Columbia University Medical Center.

"Our findings strengthen the message to patients that the pill will only work if it is taken every day. Weight does not seem to have an impact on suppression of ovulation, but consistency of pill-taking does," principal investigator Dr. Carolyn Westhoff, a professor of obstetrics and gynecology and director of the family planning division at Columbia University College of Physicians and Surgeons, said in a medical center news release.

The researchers also found that the lower-dose oral contraceptive was as effective as the higher-dose type in suppressing ovulation in obese women. This is an important finding because it was previously thought that obese women might need the higher-dose version. However, obese women are at increased risk for developing blood clots from taking birth control pills, and higher-dose pills increase that risk.

"Knowing that the lower dose works as well as the higher dose will allow physicians to not only help women with obesity avoid unwanted pregnancies, but also protect them from the possible health risks associated with higher doses," said Westhoff, who is also an obstetrician/gynecologist at New York-Presbyterian Hospital/Columbia University Medical Center.

"For a woman to fear relying on her oral contraceptive to prevent pregnancy is a huge burden. This study should put those fears to rest," Westhoff said.

The study appears in the August issue of Obstetrics & Gynecology.

More information

The American College of Obstetricians and Gynecologists has more about birth control  .

MONDAY, June 28 (HealthDay News) -- A simple blood test may one day help predict the age at which a woman will begin menopause, say the scientists who developed the test.

Their study found that the average difference between the age predicted by the test and the actual age a woman reached menopause was about four months, while the maximum margin of error was between three and four years.

If the accuracy of the test is confirmed in larger studies, women could take the test early on their reproductive life to find out their expected age at menopause, knowledge that would help them plan when to start a family, said researcher Dr. Fahimeh Ramezani Tehrani, president of the Reproductive Endocrinology Department of the Endocrine Research Centre and associate professor at Shahid Beheshti University of Medical Sciences in Tehran, Iran.

The test measures concentrations of anti-Mullerian Hormone (AMH), a hormone produced by cells in the ovaries. AMH controls the development of ovarian follicles, which contain a woman's eggs.

For their research, Tehrani and colleagues analyzed blood samples taken every few years from the participants, who also had regular physical examinations and provided information about their socioeconomic background and reproductive history.

Among the study findings:

• Early menopause (before age 45) was predicted by AMH levels of 4.1 nanograms or less per milliliter of blood at age 20, 3.3 nanograms per milliliter at age 25, and 2.4 nanograms per milliliter at age 30.
• Menopause after age 50 was predicted by AMH levels of at least 4.5 nanograms per milliliter at age 20, 3.8 nanograms per milliliter at age 25, and 2.9 nanograms per milliliter at age 30.
• The average age for menopause among women in the study was about 52.

"We developed a statistical model for estimating the age at menopause from a single measurement of AMH concentration in serum from blood samples. Using this model, we estimated mean average ages at menopause for women at different time points in their reproductive life span from varying levels of serum AMH concentration. We were able to show that there was a good level of agreement between ages at menopause estimated by our model and the actual age at menopause for a subgroup of 63 women who reached menopause during the study. The average difference between the predicted age at menopause using our model and the women's actual age was only a third of a year and the maximum margin of error for our model was only three to four years," Tehrani said in a European Society of Human Reproduction and Embryology news release.

"The results from our study could enable us to make a more realistic assessment of women's reproductive status many years before they reach menopause," said Tehrani, who presented the findings Monday at the annual meeting of the European Society of Human Reproduction and Embryology in Rome. "To the best of our knowledge, this is the first prediction of age at menopause that has resulted from a population-based cohort study. We believe that our estimates of ages at menopause based on AMH levels are of sufficient validity to guide medical practitioners in their day-to-day practice, so that they can help women with their family planning."

Tehrani added that "larger studies starting with women in their twenties and following them for several years are needed to validate the accuracy of serum AMH concentration for the prediction of menopause in young women.

William Ledger, a fertility expert at the University of Sheffield in England, who was not involved with the research, told the Associated Press: "This is not something we could start rolling out tomorrow. But if it really does work, it could be immensely useful to young women who are making choices about whether to work or have a family."

More information

The U.S. National Institute on Aging has more about menopause.