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Many people assume that brain differences between men and women result from sex hormones like estrogen and testosterone. This is not true. In fact, increasing numbers of studies find large reliable distinctions between the sexes. These effects are often seen early in development and before sex hormones are expressed. The research examining sex-specific brain mechanisms finds variability in structure, neurotransmitters, and the expression of specific genes in males and females.
Sex differences in size, shape, and function occur in every region of the brain. For example, sex divergence is seen in the hippocampus, an area of the brain that is important for learning and memory. The hippocampus makes up a larger portion of total brain size in women than in men. But that doesn’t necessarily mean that women learn better than men. Interestingly, some sub-regions of the hippocampus are larger and contain more cells in men. Further studies will be needed to fully understand the implications of such sex differences.
Additional variation occurs in the levels of neurotransmitters, the chemical messengers, in the brain. Males and females differentially produce serotonin, a neurotransmitter that affects mood. These differences may have significant effects on gender-specific treatment of diseases, such as depression.
Gene expression differences between the sexes are also seen across many species. Scientists have found groups of genes with sex-specific expression that are conserved, or maintained, across primate species, suggesting that such patterns are inherited across evolution.
What is the evolutionary advantage to having sex differences in the brain? While we can only guess, one hypothesis is that such variability is important in the selection animals make in finding mates and raising offspring. Whatever the cause, differences in the brain affect development and health during adulthood. Many of the genes with differential expression are also associated with neurological diseases such as Alzheimer’s disease, schizophrenia, and cerebral ischemia. As such, sex-specific treatments of these diseases should also be studied.
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Kate is also a frequent contributor to the Oncofertility Consortium Blog. Check it out!

A survey of more than 1,200 primary care physicians indicates that many are not following clinical practice guidelines on recommended screening intervals for cervical cancer, both with regard to traditional Pap testing as well as a newer screening method, a DNA test for the human papillomavirus (HPV). The FDA has approved HPV DNA testing for use in conjunction with Pap testing, a process called co-testing, for women age 30 and older.
At the time the survey was conducted, guidelines from the American Cancer Society and those from the American Congress of Obstetricians and Gynecologists advised extending the interval between screenings to 3 years for low-risk women over the age of 30 after three consecutive normal Pap tests or a single normal co-test (a normal Pap test plus a negative HPV DNA test). Guidelines from the U.S. Preventive Services Task Force also are consistent with a longer interval between screening tests.
In the survey, based on a hypothetical clinical vignette of a 35-year-old, low-risk woman with three prior normal Pap tests, only 32 percent of respondents reported that they would comply with guideline recommendations, researchers from the CDC and NCI reported in the June 14 Archives of Internal Medicine. Even fewer respondents, 19 percent, would comply when, during a single visit, the low-risk woman had a normal co-test result. Approximately 60 percent of those surveyed—which included general internal medicine physicians, family practice doctors, and obstetrician-gynecologists—said they would still recommend that the woman undergo annual Pap screening.
Although the Pap test is the most commonly used cervical cancer screening method, a number of studies have shown that the DNA test for HPV—the cause of the vast majority of cervical cancer cases—is more sensitive than the Pap test in detecting high-grade precancerous lesions, spurring discusions about the optimal approach to cervical cancer screening in the United States.
This new study, however, suggests that guidelines for extending screening intervals have not influenced current clinical practice, wrote Dr. Mona Saraiya of the CDC’s Division of Cancer Prevention and Control and her colleagues. “When offered the choice for HPV testing,” they wrote, “many physicians deferred to the same pattern they used for Pap testing,” annual screening with both tests or no recommendation for HPV testing.
“These practice patterns are not likely to lead to much improvement in cervical cancer outcomes, but may result in unnecessary follow-up testing, increased risk of colposcopy-associated morbidities, and distress for patients,” said Dr. Robin Yabroff, a study co-author from NCI’s Division of Cancer Control and Population Sciences.
“New HPV infections are extremely common but overwhelmingly benign; they almost always go away by themselves,” said Dr. Mark Schiffman of NCI’sDivision of Cancer Epidemiology and Genetics. “Only persistent infections are a risk factor for cancer. If you screen for HPV too often, you will detect new infections rather than persistent infections, and this poses the risk of overtreatment.”

Women who measure their peak heart rates for exercise will need to do some new math, as will physicians giving stress tests to patients.  A new formula based on a large study from Northwestern Medicine provides a more accurate estimate of the peak heart rate a healthy woman should attain during exercise. It also will more accurately predict the risk of heart-related death during a stress test.
“Now we know for the first time what is normal for women, and it’s a lower peak heart rate than for men,” said Martha Gulati, MD, assistant professor of medicine and preventive medicine and a cardiologist at Northwestern Medicine. “Using the standard formula, we were more likely to tell women they had a worse prognosis than they actually did.”   Gulati is the lead author of a study published June 28 in the journal Circulation.
“Women are not small men,” Gulati added. “There is a gender difference in exercise capacity a woman can achieve. Different physiologic responses can occur. ”   Gulati was the first to define the normal exercise capacity or fitness level for women in a 2005 study.
The old formula — 220 minus age — used for almost four decades, is based on studies of men. The new formula for women, based on the new research, is 206 minus 88 percent of age.   At age 50, the original formula gives a peak rate of 170 beats per minute for men and women. The new women’s formula gives a maximum heart rate of 162 beats for women.  Many men and women use their peak heart rate multiplied by 65 to 85 percent to determine their upper heart rate when exercising.
“Before, many women couldn’t meet their target heart rate,” Gulati said. “Now, with the new formula, they are actually meeting their age-defined heart rate.”    The new formula is trickier to calculate, Gulati acknowledged, but is easily determined with a calculator. She currently is working on an iPhone application for a quick calculation.
The new formula is based on a study of 5,437 healthy women ages 35 and older who participated in the St. James Women Take Heart Project, which began in the Chicago area in 1992.    With the new formula, physicians will more accurately determine if women are having a normal or abnormal response to exercise.    “If it’s abnormal, that’s a marker for a higher risk of death,” Gulati said. “Maybe we need to talk about whether you exercise enough and what we need to do to get it into the normal range.
“We need to keep studying women to get data applicable to women,” Gulati said. “It’s important to not get complacent that we have data on men and assume women must be the same. They’re not.”
Gulati’s senior author on the study was the late Morton Arnsdorf, MD, professor emeritus and associate vice chairman of medicine and former section chief of cardiology at the University of Chicago.

The following press release was issued by the FDA. While the seriousness and pain of bone fractures is significant, the side effect profiles of this drug sound pretty serious.   What is the risk/benefit ratio?   Is the trade-off worth it?  We would love to hear from women who are making these choices.
JUNE 1, 2010:   The U.S. Food and Drug Administration today approved Prolia, an injectable treatment for postmenopausal women with osteoporosis who are at high risk for fractures.
Osteoporosis is a disease in which the bones become weak and are more likely to break. According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases, 80 percent of the people in the United States with osteoporosis are women. One out of every two women over age 50 will break a bone in their lifetime due to osteoporosis.
People with osteoporosis at high risk for fracture include those that have had an osteoporotic fracture, or have multiple risk factors for fracture; or those who have failed or are intolerant to other available osteoporosis therapy. Prolia works to decrease the destruction of bone and increase bone mass and strength. An injection of Prolia is recommended once every six months.
“Due to its prevalence, osteoporosis is a serious concern to public health,” said Julie Beitz, M.D., director of the FDA’s Office of Drug Evaluation III. “The approval of Prolia provides another treatment option for postmenopausal women with osteoporosis who are susceptible to fractures.”
The safety and efficacy of Prolia in the treatment of postmenopausal osteoporosis was demonstrated in a three-year, randomized, double-blind, placebo-controlled trial of 7,808 postmenopausal women ages 60 to 91 years. In the study, Prolia reduced the incidence of vertebral, non-vertebral, and hip fractures in postmenopausal women with osteoporosis.
The most common side effects reported with Prolia include back pain, pain in the extremities, musculoskeletal pain, high cholesterol levels, and urinary bladder infections. Serious adverse reactions include hypocalcaemia (low calcium levels in the blood), serious infections, including infections of the skin, and dermatologic reactions such as dermatitis, rashes, and eczema.
Prolia causes significant suppression of bone turnover and this suppression may contribute to the occurrence of osteonecrosis of the jaw, a severe bone disease that affects the jaw, atypical fractures, and delayed fracture healing.
Prolia was approved with a risk evaluation and mitigation strategy (REMS) that includes a Medication Guide for patients and communications to health care providers that explains the risks and benefits of the drug.
Prolia is manufactured by Amgen Manufacturing Limited, a subsidiary of Thousand Oaks, Calif.-based Amgen Inc.
For more information about osteoporosis click here.