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T4, or thyroxine, is the main hormone secreted by the thyroid gland. Thyroid hormones are responsible for a range of bodily functions, including metabolism and growth. The amount of T4 produced is controlled by TSH (thyroid-stimulating hormone), and free T4 is a measure of the amount of thyroxine that is unbound to proteins in the blood. (source)
Low free T4 levels can be influenced by physiological factors relating to the thyroid gland, which produces T4. From a nutritional perspective, dietary levels of essential nutrients like iodine and selenium can affect thyroid hormone production and function, potentially leading to lower free T4 levels. (source, source, source, source)
Limit selenium-rich foods: Consumption of selenium has been shown to reduce free T4 levels. (source, source) Selenium is an essential component of compounds that convert T4 to T3. (source, source) Limiting the consumption of selenium decreases free T4 levels. Recommendation: Monitor and limit excess consumption of selenium-rich foods, like organ meats, seafood, and Brazil nuts.
Prioritize sleep: Restricted sleep duration has been associated with lower free T4 levels. (source) Sleep deprivation has been shown to suppress the secretion of thyroid-stimulating hormone, thus reducing free T4. (source) Prioritizing sleep regulates free T4 concentrations. Recommendation: Strive to get 8 to 10 hours of sleep for optimal recovery and adaptation.
Avoid selenium: Supplementation with selenium has been shown to reduce free T4 levels. (source, source) Selenium plays a key role in the conversion of T4 to T3. (source, source) Limiting the intake of selenium decreases free T4 levels. Recommendation: Monitor intake and supplement concentrations.
High free T4 levels can often be attributed to physiological factors related to thyroid gland function, as the thyroid gland produces and releases thyroxine (T4). Additionally, physiological factors relating to the liver, the site of thyroid-binding globulin production, can influence free T4 levels. Nutritional factors such as iodine and selenium intake can play a crucial role in thyroid hormone synthesis and regulation. (source, source, source, source)
Prioritize selenium-rich foods: Consumption of selenium has been shown to reduce free T4 levels. (source) Selenium is an essential component of compounds that convert T4 to T3. (source, source) Consuming foods rich in selenium decreases free T4 concentrations. Recommendation: Eat at least one serving of selenium-rich foods three times per week.
One serving examples: Brazilian Nuts (1 oz), Yellowfin Tuna (3 oz), Sardines (3 oz), Beef (3 oz), Chicken (3 oz)
Avoid cold exposure: Cold exposure has been shown to increase free T4 levels. (source) Exposure to extreme cold decreases thyroid hormone-binding capacity, resulting in increased levels of free T4. (source) Limiting exposure to cold aids in regulating free T4 concentrations. Recommendation: Limit exposure to cold temperatures.
Supplement with selenium: Supplementation with selenium has been shown to reduce free T4 levels. (source) Selenium plays a key role in the conversion of T4 to T3. (source, source) Supplementing with selenium decreases free T4 concentrations. Recommendation: Supplement with at least 50 mcg of selenium.
