A new study published by USF researchers in Climacteric, the Journal of the International Menopause Society, showed that progestin, a synthetic progesterone hormone, may be the cause of harmful side effects reported by women who receive hormone replacement therapy.

In the study, a novel imaging technique designed by two USF professors in the anatomy department, Tom Thomas and Johannes Rhodin, was used to show that progestin causes damage to blood vessels in the body which lead to an increase in the incidence of heart attacks, strokes and memory problems.

“The study was done to show what works better for women, that progesterone and estrogen are good, but that synthetic progestin is more damaging than helpful,” Rhodin said.

Progesterone is a natural gestational hormone found in the body, and high levels of the hormone can be found in the body during pregnancy. The difference between progesterone and progestin, said Thomas, is that progesterone is a natural hormone in the body that metabolizes quickly, while progestin is a synthetic version of the hormone that cannot be broken down easily.

“I think the two molecules are different. (With) the natural progesterone, the body is able to handle it, and I think the synthetic progestin is somehow triggering an inflammation and blood vessel damage,” Thomas said.

The imaging technique used in the study employed fluorescence, in a combination with video and electron microscopy, to label blood cells in order to observe blood flow, blood vessel structure and the activities of various blood cells in rats.

In the study, a menopause-like situation was created in rats and then estrogen, progesterone and progestin were administered. Thomas and Rhodin found that when estrogen or progesterone was used there was no damage to blood vessels or high levels of toxicity. But when progestin was used they found visible damage to the periphery and brain blood vessels, endothelial and smooth muscle damage, inflammation and blood clot formation and impeded blood flow.

The results of this study contradict the results of a study done one year earlier by the National Institute of Health. The study done by the NIH, which was sponsored by the Women’s Health Initiative, showed that estrogen in a combination with progestin caused high levels of toxicity and blood vessel damage resulting in increased occurrences of heart attacks, strokes and Alzheimer’s disease. This study caused thousands of women to stop using estrogen, which was thought to be the cause of the high levels of toxicity and damage to the blood vessels.

“Last year was the most dramatic change in medical treatment in modern history because women felt that maybe they shouldn’t take these medications because they might get cancer or a stroke,” Rhodin said.

Thomas and Rhodin worked on the novel imaging technique for three years before it was finished. It was originally developed to investigate the causes of Alzheimer’s disease. One of the first projects that Thomas and Rhodin worked on was looking at a protein, amyloid-beta, that built up in the brain of Alzheimer’s patients.