tsh
7 interactions related to tsh
levothyroxine + biotin
High-dose biotin (B7) does not directly interact with levothyroxine pharmacologically, but it interferes with biotin-streptavidin immunoassays used for TSH, free T4, free T3, and thyroglobulin. This can produce falsely low TSH and falsely high T4/T3, mimicking hyperthyroidism and leading to inappropriate dose reductions.
levothyroxine + soy
Soy protein and isoflavones can bind to levothyroxine in the gut and reduce its absorption, sometimes increasing dose requirements in hypothyroid patients. Case reports and systematic reviews describe rising TSH and unstable thyroid levels in patients consuming soy products close to their dose.
levothyroxine + ashwagandha
Ashwagandha (Withania somnifera) can increase serum T3 and T4 and lower TSH, effectively adding to the thyroid hormone effect of levothyroxine. Case reports describe patients on stable levothyroxine who developed thyrotoxicosis and even painless thyroiditis after starting ashwagandha.
tempeh + levothyroxine
Tempeh is a fermented soybean cake, and soy protein binds levothyroxine in the gut and reduces its absorption, with documented decreases of 16 percent at 20 grams of soy protein and over 35 percent at 40 grams. Fermentation reduces isoflavone bioavailability but leaves intact soy protein that still interferes with thyroid hormone uptake.
edamame + levothyroxine
Edamame is whole young soybeans, and the soy protein and isoflavones bind levothyroxine in the gut and reduce its absorption, with measured drops of 16 percent at 20 grams of soy protein and over 35 percent at 40 grams. A one-cup serving of shelled edamame supplies roughly 18 grams of soy protein, enough to cause clinically meaningful interference if eaten close to the dose.
biotin + thyroid stimulating hormone test
High-dose biotin interferes with biotin-streptavidin-based immunoassays used to measure TSH, free T3, free T4, and thyroglobulin, producing a falsely low TSH and falsely elevated free thyroid hormones, a pattern that mimics Graves' disease. Patients have been incorrectly diagnosed with hyperthyroidism and started on antithyroid drugs because of biotin interference.
tofu + levothyroxine
Tofu is made from coagulated soy milk and is one of the most concentrated sources of soy protein in the typical diet, with roughly 20 grams of soy protein per cup. Soy protein binds levothyroxine in the gut and reduces absorption by 16 to over 35 percent depending on dose, and case reports describe TSH rising when tofu is added to a previously stable levothyroxine regimen.