Microplastics are a well known environmental concern, but understanding how these tiny particles affect human hormonal function is still in its early stages. These microplastics are created as plastic products degrade, including plastics from trash, fabrics, cleaning products, containers, and cosmetics, but can also be present in produce, seafood, and other food products. Due to their size, the concern is that they can infiltrate various body tissues, with scientists documenting recordable levels in human blood and saliva as well as organ tissues such as the liver, kidneys, and placenta. Even smaller particles, known as nanoplastics, have the potential to enter human cells, resulting in a host of additional effects (1).
The health concerns regarding these micro and nano plastics can range, with evidence indicating potential DNA damage, oxidative tissue damage, changes in gene activity, and risk for cancer development. With that in mind, a lot of the focus regarding the detrimental effects of these particles looks at how they can affect the endocrine system, including the hormonal function of the reproductive system in both men and women (1).
Currently, much of what is known in the scientific community comes from animal studies with numerous rodent studies implicating microplastics in reproductive concerns, especially infertility or sub-fertility. For example, oral microplastic exposure in mice has been shown to cause an accumulation of these particles in both the ovaries and testes of these animals. In the ovaries, these mice showed a reduced number of follicles and anti-mullerian hormone levels (a hormone related to fertility status). There were also indicators of oxidative stress and an inflammatory response within the ovary. In male mice, exposure to microplastics resulted in lower serum testosterone, lower sperm count, and an increased number of abnormal sperm cells, all of which are important to fertility status (2).
With microplastics being able to infiltrate the ovaries and testes of mammals, it is no surprise that they have the potential to interfere with reproductive hormone production lowering estrogen, progesterone, and testosterone levels. An additional concern however is that these microplastics can act as a transport medium for plastic-additives that are known endocrine disrupting chemicals (ie. BPA). These additives have shown to contribute to infertility, promote the growth of hormone-based tumors, and disrupt normal metabolism all via disruption of hormone function (3). Therefore, though at base microplastics lower reproductive hormones, were there are additional chemicals that can worsen this or disrupt the normal function of what is produced.
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That being said, hormones are not restricted to the reproductive system; they are body-wide with numerous essential functions. Another incredibly important gland that can be affected by the accumulation of microplastics is the thyroid gland, which controls the body’s brain function, growth/metabolism, and neurological development. Exposure to these molecules has been shown in studies to reduce thyroid hormone levels, affect the binding of thyroid hormone to its necessary receptors, and cause changes in the thyroid tissue itself (ie. Hyperplasia of cells). As with the reproductive system, the chemical additives present in these microplastics can also contribute heavily to these disruptions (3).
Overall, it appears in mammalian studies that exposure to these microplastics result in a build up within glandular tissue. This results in inflammatory damage that generally results in a decline in the production of the gland's intended hormone. However, the microplastics alone aren’t the only issue; the endocrine disrupting chemicals found as additives in these microplastics can also contribute in various ways to hormonal problems whether that be in production, tumor growth, or disruption in normal hormone metabolism. Teasing out exactly how these molecules affect hormone health, especially in humans will take more time but it is clear that they are not harmless to the human body and efforts should be taken to reduce exposures.
At AYUMETRIX we hope to provide easy access to data that represents an individuals’ health, including hormone and environmental toxin levels. With this information both providers and patients can feel confident in their treatment plans and how best to navigate a very complicated physiology and environment. For more information please visit www.ayumetrix.com.
References: 1. Dutchen, Stephanie. “Microplastics Everywhere” Harvard Medicine. Spring 2023.
2. Yang, J., Kamstra, J., Legler, J., Aardema, H. 2023. The impact of microplastics on female reproduction and early life. Anim Reprod. 20(2): e20230037
3. Ullah, S., Ahmad, S., Guo, X., Ullah S., Ullah, S., Nabi, G., Wanghe. K. 2023. A review of the endocrine disrupting effects of micro and nano plastic and their associated chemicals in mammals.
