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Thyroid hormones circulate in the blood bound to transport proteins (called thyroid-binding globulins, or TBG). T3 uptake is used as an indirect measure of TBG binding capacity. (source, source)
Low T3 uptake can result from physiological factors affecting thyroid hormone metabolism. Other factors affecting the liver, the site of thyroid-binding globulin production, can also affect T3 uptake measures. Nutritionally, deficiencies in essential nutrients like selenium and iodine, which are vital for thyroid hormone production, can contribute to reduced T3 uptake. (source, source, source)
Limit selenium-rich foods: Consumption of selenium has been shown to negatively affect free T4, which is related to T3 uptake. Selenium allows for the conversion of the inactive thyroid hormone T4 into the active form T3, thereby decreasing free T4 levels (source) Limiting selenium intake can help support 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, which is associated with T3 uptake. (source) Sleep deprivation contributes to the suppression of TSH and T4 levels. (source) Recommendation: Strive to get 8 to 10 hours of sleep for optimal recovery and adaptation.
Avoid selenium: Consumption of selenium has been shown to negatively affect free T4, which is related to T3 uptake. (source) Selenium allows for the conversion of the inactive thyroid hormone T4 into the active form T3, thereby decreasing free T4 levels. (source) Limiting selenium intake can help support free T4 levels. Recommendation: Monitor intake and supplement concentrations.
High T3 uptake can often be attributed to physiological factors related to thyroid function and hormone regulation, as the thyroid gland plays a central role in producing thyroid hormones. Physiological factors affecting the liver, the site of thyroid-binding globulin production, can also affect T3 uptake measures. From a nutritional perspective, iodine intake and selenium status can influence T3 uptake. (source, source, source)
Prioritize selenium-rich foods: Consumption of selenium has been shown to negatively affect free T4, which is related to T3 uptake. (source) Selenium allows for the conversion of the inactive thyroid hormone T4 into the active form T3, thereby decreasing free T4 levels (source) 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)
Supplement with milk thistle: The liver plays an important role in thyroid hormone conversion. (source) Taking supplements to support its health can help optimize levels. Recommendation: Supplement with at least 420 mg of milk thistle daily.
