The hormone cream estradiol can repair aging skin, but only if the damaging ultraviolet rays of the sun have never touched that skin, new research finds.
Decades of sun damage on the face and arms and other exposed areas seem to undermine the power of the cream, according to a study in the Archives of Dermatology.
Unfortunately, these are the exact areas that are most in need of repair.
"There was a general belief that estrogen was good for the skin," explained study author Laure Rittié, PhD, a research investigator in the department of dermatology at the University of Michigan Medical School in Ann Arbor. But most, if not all, previous studies that had purported to show this looked at sun-protected areas of the skin, not sun-exposed areas.
"When we look for treatments for aging skin, we usually want to treat the face or hands or neck-in other words, sun-exposed areas," Dr. Rittié explained. "We decided to go ahead and carefully test these questions."
Researchers applied topical estradiol for two weeks to both sun-exposed areas on the forearm and non-exposed skin near the hip in 40 women and 30 men, average age 75.
A biopsy was taken from each volunteer 24 hours after the last treatment. The study was partially supported by Pfizer.
The cream stimulated collagen production in sun-protected skin areas but not in sun-damaged areas. The collagen-promoting effects were found in both men and women but were more pronounced in women volunteers.
"Despite commonly held beliefs, estrogen was not able to raise collagen when the skin was damaged by sunlight," said Dr. Rittié. "Apparently, chronic exposure to sunlight breaks something in the way estrogen increases collagen, which makes damaged skin even harder to repair.
The authors acknowledge that treating volunteers for more than two weeks might have yielded different results in sun-exposed skin areas; additional studies would be needed to test this.
"What makes a hormone a hormone is that it is made in one place but works somewhere else in the body," said Doris Day, MD, an attending physician in dermatology at Lenox Hill Hospital in New York City. "It's like a light switch; it's small but, when you turn it on, the whole room lights up. Estradiol cream is like a little switch, but we're only just beginning to understand the different parts of the body it affects and how it affects them. This is putting the science behind the anecdote."