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Written by: Lauren Chamberlain
Edited and Reviewed By: Anabelle Clebaner MS, RDN
Iodine is a powerhouse nutrient that plays a vital role in thyroid function, hormone balance, and reproductive health. Despite its importance, many people—especially women—don’t get enough of it, leading to potential health complications. Beyond its well-known effects on thyroid function, recent research suggests that iodine plays a role in glucose metabolism, insulin sensitivity, and fertility. In this post, we’ll explore iodine’s impact on the body, its connection to thyroid and reproductive health, and why you should consider testing your iodine levels!
The thyroid gland depends on iodine to produce hormones that regulate metabolism, energy levels, and overall endocrine balance. Here’s how it works:
When you consume iodine, it gets absorbed in the gastrointestinal tract and transported to the thyroid via the sodium-iodide symporter (NIS). If your body detects low thyroid hormone levels, the pituitary gland releases thyroid-stimulating hormone (TSH) to prompt the thyroid to absorb iodine and produce more T4, which then converts into the active T3.
A rise in TSH after starting iodine supplements is often misunderstood. TSH stimulates more NIS molecules, helping transport iodine into thyroid cells. A temporary increase in TSH is a normal response, not necessarily a sign of thyroid dysfunction. However, excessive iodine intake can paradoxically impair thyroid function by triggering hypothyroidism or autoimmune thyroiditis. This is why careful monitoring through the use of a health professional is essential.
Beyond the thyroid, iodine plays a crucial role in reproductive health, hormone balance, and even breast tissue integrity. Here’s how:
Iodine is essential for ovarian function because the ovaries store a lot of iodine because our growing follicles take up iodine to grow properly. Studies suggest that iodine deficiency may contribute to menstrual irregularities and impaired ovulation, potentially affecting fertility.
Iodine helps regulate estrogen metabolism by promoting the breakdown of estrogen into more favorable metabolites. This may help reduce inflammation, fibrocystic breast changes, and the risk of estrogen-dominant conditions like endometriosis.
Iodine accumulates in breast and uterine tissues, where it supports cellular integrity and may protect against fibrocystic breast disease. A deficiency in iodine has been linked to an increased risk of breast cancer due to impaired estrogen metabolism and oxidative stress.
Iodine is crucial during pregnancy, as it supports fetal brain development, prevents cretinism, and reduces the risk of miscarriage and low birth weight. A deficiency in pregnancy can lead to intellectual disabilities, developmental delays, and even maternal hypothyroidism, which can have long-term effects on the child.
Iodine belongs to the halogen family, which includes fluorine, chlorine, and bromine. Unfortunately, these elements have similar chemical makeups so they compete with iodine for absorption and can erroneously bind to iodine receptors, potentially leading to deficiency:
This means that even if you consume iodine-rich foods, environmental exposure to these halogens could impact absorption.
Emerging research suggests that iodine may play a crucial role in glucose metabolism and insulin sensitivity. One potential mechanism involves iodine’s interaction with peroxisome proliferator-activated receptor-γ (PPAR-γ), a nuclear receptor that regulates lipid and glucose metabolism. PPAR-γ activation has been associated with improved insulin sensitivity by enhancing glucose uptake in peripheral tissues and modulating adipocyte differentiation. This suggests that iodine may contribute to metabolic health by influencing pathways that regulate insulin signaling.
However, the relationship between iodine and glucose metabolism is complex. While adequate iodine intake may support insulin function, excessive iodine consumption has been linked to cytotoxic effects on pancreatic beta cells, which are responsible for insulin secretion. High iodine levels can induce oxidative stress and apoptosis (cell death) in these cells, potentially impairing insulin production and increasing the risk of glucose dysregulation. Additionally, iodine excess has been associated with thyroid dysfunction, which can indirectly affect insulin sensitivity and glucose homeostasis through alterations in thyroid hormone levels.
These findings highlight the need to maintain optimal iodine intake, as both deficiency and excess can have metabolic consequences. Further research is needed to clarify the precise mechanisms by which iodine influences insulin function and to determine safe and effective dietary recommendations for individuals at risk of metabolic disorders.
While iodine deficiency can affect anyone, certain populations are at higher risk:
If you suspect iodine deficiency, a urinary iodine clearance test can help assess your levels. We only absorb 10% of iodine in the gut when levels are sufficient, so we want 90% excreted in the urine.
Relying on TSH alone isn’t enough to evaluate thyroid function. If you’re experiencing fatigue, weight gain, cold intolerance, or brain fog, consider testing:
Before making changes to your iodine intake—whether through food sources or supplements—it’s essential to establish a strong foundation for overall health. Iodine metabolism is influenced by multiple factors, including stress, sleep, and nutrient status, so addressing these areas first can help your body utilize iodine more effectively. Consulting with a healthcare professional is also key to ensuring that supplementation is appropriate for your individual needs.
Consider these important questions before increasing iodine intake:
Am I eating enough?
Am I under high stress?
Am I getting proper light exposure and balancing my circadian rhythm?
Am I getting quality sleep?
Am I going through a particularly demanding or stressful season of life?
Am I deficient in other key minerals?
Since iodine is just one piece of the puzzle, it’s crucial to build a strong nutritional and lifestyle foundation before increasing intake. Addressing these factors first will help your body better absorb and utilize iodine while minimizing potential risks associated with excess or imbalance.
Iodine supplementation isn’t a one-size-fits-all approach. Here are some key factors:
Signs of iodine deficiency can be subtle but may include:
To maintain healthy iodine levels, include these foods in your diet:
Iodine is an essential yet often overlooked nutrient that plays a pivotal role in thyroid function, hormone balance, metabolic health, and reproductive function. If you struggle with fatigue, hormonal imbalances, insulin resistance, or fertility concerns, it may be worth assessing your iodine levels and ensuring you’re getting enough from your diet or supplements. However, balance is key—too much iodine can be just as harmful as too little.
By understanding how iodine influences your health, you can take proactive steps to optimize your intake and support overall well-being.
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