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Release: Jan. 7, 2003

UI researchers study effects of menstrual cycle on diabetes

People with type 1 diabetes work hard to control their blood sugar levels by balancing food intake, exercise and insulin doses. Young women with diabetes have another and poorly understood variable -- the menstrual cycle -- that can make their diabetes more challenging to control.

However, University of Iowa Health Care investigators are using new technology to learn why women with diabetes may need to increase or decrease insulin doses during their menstrual cycle. The pilot program underway in the Division of Endocrinology-Metabolism in the UI Department of Internal Medicine takes advantage of a device that can monitor blood sugar (glucose) levels continuously throughout the complete menstrual cycle. The goal is to learn more about how the menstrual cycle affects glucose control, and potentially advise each woman with type 1 diabetes how much insulin she specifically needs at different points in her menstrual cycle.

"We decided to do this study because there is not a lot of conclusive data on the effects of the menstrual cycle on blood glucose control, specifically for women with type 1 diabetes," said Whitney Goldner, M.D., UI endocrinology fellow in internal medicine. "However, many women with type 1 diabetes tell us that they notice changes in their blood glucose levels at different times of their cycle and that this variability can be part of the problem in getting their sugars under control."

Goldner said that some women report blood sugar levels higher than normal (hyperglycemia) while others report levels lower than normal (hypoglycemia) at various times in the menstrual cycle, even when the insulin being used is the same amount that effectively controlled the glucose levels on a prior day. It is important for people with diabetes to control their blood sugar levels, otherwise very low sugars can lead to blackouts or seizures, and high sugars over many years can cause damage to the nerves, eyes, kidneys, heart and other organs.

Goldner and co-investigator Joseph Dillon, M.D., UI assistant professor of internal medicine, said the pilot study is exciting because it uses a portable device that measures glucose levels in the tissue every five minutes. Previous related studies used only a fixed point in time, e.g., 10:30 a.m., on a specific day or several days during the menstrual cycle.

"Previously, women had to come to a hospital and be hooked up to an I.V. to get this type of data," said Dillon, who also is a researcher and staff physician with the Iowa City Veterans Affairs Medical Center (VAMC). "In contrast, the continuous glucose monitors are practical to wear, and we can actually get the data on a continuous basis. The participants are doing extremely well using the monitor."

The monitor is similar to an insulin pump, which some people with diabetes use to receive their daily insulin doses. About the size of a pager, the device is worn on a belt or around the waist. A small plastic needle, attached to fine tubing, is inserted under the skin of the abdomen, and delivers data to the recording part of the device. The information then is periodically downloaded to a computer and analyzed for patterns, including connections to menstruation-related hormones.

"In addition to plotting out the glucose measurements, we are analyzing different hormone levels measured at various points in the cycle to see if there are any correlations between these hormone levels and glucose control," Goldner said. "Certain hormone levels change during different points in the menstrual cycle. We are investigating whether this may be one reason for changes in glucose control."

Goldner and Dillon expect to complete the pilot study by April 2003 and report results later in the year.

Other investigators on the study are Vicki Kraus, Ph.D., UI nurse practitioner in internal medicine; William Sivitz, M.D., UI professor of internal medicine and a staff physician and researcher with the Iowa City VAMC; and Stephen Hunter, M.D., Ph.D., professor of obstetrics and gynecology.

Type 1 diabetes affects nearly 1 million people in the United States. The condition most commonly begins in childhood or adolescence, however, it can also develop in adulthood. The condition develops when there is destruction of certain pancreatic cells that are the sole source of insulin -- the hormone that regulates blood sugar. Genetic and environmental factors can both contribute to type 1 diabetes.

University of Iowa Health Care describes the partnership between the UI Roy J. and Lucille A. Carver College of Medicine and UI Hospitals and Clinics and the patient care, medical education and research programs and services they provide. Visit UI Health Care online at www.uihealthcare.com.