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<\/figure>\n<\/div>\n\n\nNature<\/em><\/strong> here is our genes<\/mark>, our DNA that we inherited from our mother and father. This idea holds that our personality, our other traits and tendencies are scribed in our genes. “Nature” is when we look at relatives with cancer or schizophrenia and we worry that we’ll end up that way because “it runs in the family.”<\/p>\n\n\n\n Nurture<\/em><\/strong>, on the other hand, is the idea that we are products of our environment<\/mark>. That being around a family that eats a lot of junk food and are overweight means that we are likely to eat a lot of junk food and be overweight. That our upbringing and experiences early in life shape who we become.<\/p>\n\n\n In fact, it turns out these both<\/em><\/strong> are powerful aspects in our development, beginning before we are fertilized embryos throughout our infancy, childhood, adulthood and old age.<\/p>\n\n\n\n “Nature” and<\/em><\/mark><\/strong> “Nurture” both play a huge role, as collaborators, in who and what we become and what we continue to be. Let’s get into this a little bit, by considering thyroid hormone<\/em><\/strong>.<\/p>\n\n\n\n Our bodies are amazing<\/mark><\/strong>, if you stop and think about it. We have all these organs and tissues – lungs, heart, brain, gut, liver, kidneys, muscles. They are separate and yet they work together like a smooth, complex super machine so that we walk, talk (often at the same time!), eat food and digest it, and on and on. Ever wonder how we achieve this coordination? For that matter, how do our organs, bones and muscles all somehow seem to grow together as we grow up? We don’t have situations where, let’s say, our feet grow to adulthood years before our heads or upper body catch up. In another example, we’d get pretty sick (or die) if we used up all the blood sugar in our blood during exercise<\/p>\n\n\n and didn’t somehow maintain a supply that lasts til we eat a meal. How do all these body functions work smoothly together to meet our needs?<\/p>\n\n\n\n Our brains work with our hormones to coordinate our body functions<\/mark><\/em><\/strong><\/p>\n\n\n\n Our brains play a huge role in coordinating our body’s functions- with a nervous system that is a massive web that interconnects our cells and tissues and organs. But we also have a chemical messenger system of hormones<\/mark><\/strong> (called our endocrine system) that travel through our blood to coordinate activities like growth, metabolism, development\/aging, periods of fasting, response to stress and much more. These hormone messengers originate in our brain, but also in various organs and glands. Here is a fairly simple image of one hormone messenger system, thyroid hormone<\/strong>. The image is from the Cleveland Clinic<\/a>.<\/p>\n\n\n\n Thyroid hormones (T3\/T4) are kept at very constant levels by a regulatory feedback loop, a common scheme for many of our hormones. A region of the brain called the hypothalamus is sometimes called a “master gland” because it makes and releases regulatory hormones into the brain’s blood supply, acting on a tiny gland at the base of the brain, where our optic nerves cross, called the pituitary gland. This gland releases hormones into the general blood supply, to act on the various glands to control their production and release of hormones. So, for thyroid hormone, the pituitary gland releases TSH (thyroid stimulating hormone) that acts on the thyroid gland, which is around the top of our windpipe (below our tonsils). The thyroid hormone itself acts back on the pituitary gland and the hypothalamus to regulate the release of their hormones, like a thermostat regulates our house temperature.<\/p>\n<\/div>\n<\/div>\n\n\n\n Thyroid hormone (which is actually two different messengers that work together, T3 (triiodothyronine) and T4 (thyroxine)), is crucial for our development before we are born and during childhood, and is also essential over our entire lives, helping to regulate our body metabolism, resting heart rate, body temperature, skin and bone health, among many other functions. Early in development, before we are born, thyroid hormone coming from our mother’s blood supply through the placenta plays a key role in our early brain and heart development. The thyroid gland begins its development early, but it is not fully functional until the last half of pregnancy. It develops before the brain and well before the pituitary\/hypothalamus control system. This means that thyroid hormone production in fetal development is dependent on the placenta and maternal blood supply and so is vulnerable to any outside chemicals that the mother is exposed to that can gain access to the fetus through the placenta. And then, after birth, the thyroid system continues to be sensitive to chemicals that we may breathe, eat or rub on our skin, over the course of our lives.<\/p>\n\n\n\n Chemicals in our Environment can Alter Thyroid Hormone Function<\/mark><\/em><\/strong><\/p>\n\n\n\n The chemicals that can alter how a hormone system works are called Endocrine Disrupting Chemicals (EDCs). We get exposed to chemicals in the air we breathe, the food we eat, the water we drink, and things we rub on our skin. Many different kinds of chemicals can change how our thyroid hormone system works- decreasing its function or increasing its function– depending on the amount of the chemical, the time when we are exposed and for how long or how many different times. We are exposed to hundreds of chemicals, in a complex and changing mixture. Here’s just a few examples of the types of chemicals that disrupt our thyroid function, that are very common to most of us:<\/p>\n\n\n\n It’s pretty obvious from this list that these disrupting chemicals are found in every aspect of our modern lives. Most of us seem okay despite all these chemicals, right? But, if we take a closer look, we notice that many of us are experiencing health and neural effects, most likely from the constant exposure to the chemical stew around and inside of us.<\/p>\n\n\n A 2021 article published by scientists at a prominent university in Croatia<\/a> noted that the incidence of thyroid cancers and thyroid diseases have increased in the past 20-30 years. The American Thyroid Association<\/a>, also in 2021, reported that more than 12% of the US population has been or will be diagnosed with a thyroid disease during their lifetime and they estimated that more than 20 million US citizens have some form of thyroid disease. While most are readily treatable, the economic cost to the US, just from low thyroid function<\/a> disease in the US among adults runs over $2 billion– in medical costs, work absenteeism, and long-term disability. And that doesn’t include thyroid-related neurodevelopmental issues, or thyroid cancers, or hyperthyroidism (overactive thyroid disease).<\/p>\n\n\n\n In 2019, a prominent scientist and expert in endocrine disrupting chemical effects, Barbara Demeneix<\/a>, published an important paper<\/a> in the European Thyroid Journal <\/em>that examined a huge amount of accumulating evidence that thyroid hormone disrupting chemicals<\/mark><\/strong> are likely responsible for a worrying increase in neurodevelopmental issues in kids, like Autism Spectrum Disorder, ADHD, and various learning disabilities. Other developmental problems included soaring childhood obesity, precocious puberty, asthma and allergies. These kids were exposed to the chemicals before they were born and during infancy and early childhood. As the kids got older, there was also an increase in the incidence of childhood anxiety and depression, as well as speech and hearing issues and reduced verbal comprehension on school examinations. <\/p>\n\n\n\n![\"\"](\"https:\/\/earthmoves.vassarspaces.net\/wp-content\/uploads\/2023\/06\/communityjpg.jpeg\")
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