Can Sunscreen Make You Hypothyroid?
Study Shows UV Filters May Disrupt Hormone Production
According to research being presented at the European Congress of Endocrinology in Glasgow, Scotland, there is evidence from animal studies that the chemicals used in sunscreens and some anti-aging products may disturb thyroid function.
The chemical studied was 4MBC, which absorbs ultraviolet radiation, along with benzophenone 2 (BP2). The animal studies treated rats with 4MBC for 5 days, which significantly increased levels of thyroid stimulating hormone (TSH), with unchanged T3 and slightly lower T4. These are changes that are “typical of the early stages of hypothyroidism,” according to the study’s leader Professor Josef Köhrle.
The weight of the thyroid glands also increased significantly, another sign of thyroid dysfunction.
Interestingly, the thyroid results were prevented if there was adequate iodine in the mixture.
The researchers stress that the results have only been shown on animals to date, but that similar human studies will be done.
According to Professor Köhrle:
The work has shown that MBC and BP2 are potent disruptors of the pituitary-thyroid hormonal system in rats. It’s early days, but if the same effect is discovered in humans, then we may have to rethink how we protect children and those with existing thyroid problems or those in iodine-deficient areas from sun exposure.
It’s important to note that the chemicals were fed to the rats — because surveys in many areas have shown these chemicals in the water supplies, but these studies were not of topically applied chemicals that enter the blood via the skin.
At present however, most experts agree that any theoretical thyroid risks of sunscreen outweigh the known benefits.
Professor Köhrle suggested that people not give up sunscreen, but instead, make sure their diet includes enough iodine.
Source: Professor Köhrle presented the findings at the 2006 European Congress of Endocrinology.
Mary Shomon, About.com’s Thyroid Guide since 1997, is a nationally-known patient advocate and best-selling author of 10 books on health, including “The Thyroid Diet: Manage Your Metabolism for Lasting Weight Loss,” “Living Well With Hypothyroidism: What Your Doctor Doesn’t Tell You…That You Need to Know,” “Living Well With Graves’ Disease and Hyperthyroidism,” “Living Well With Autoimmune Disease,” “Living Well With Chronic Fatigue Syndrome and Fibromyalgia,” and the “Thyroid Guide to Fertility, Pregnancy and Breastfeeding Success.”