tsh
7 interactions related to tsh
levothyroxine + biotin
Biotin (vitamin B7) does not interact with levothyroxine pharmacologically and does not change how the medication is absorbed or works. The issue is in the lab: high-dose biotin can interfere with the biotin-streptavidin immunoassays used to measure TSH, free T4, free T3, and thyroglobulin, which can produce a falsely low TSH and falsely high T4/T3 pattern that mimics an overactive thyroid and can prompt an inappropriate dose change.
levothyroxine + soy
Soy protein and isoflavones can bind to levothyroxine in the gut and reduce how much of the dose is absorbed, which can raise TSH and, in some people, increase the dose needed to stay in range. The effect is most relevant with large, variable soy intake taken close to the dose, and is best documented in infants fed soy formula.
levothyroxine + ashwagandha
Ashwagandha (Withania somnifera) can lower TSH and raise T3 and T4, so it acts on your own thyroid axis on top of the levothyroxine you already take. A randomized trial showed this hormone shift in people with subclinical hypothyroidism, and separate case reports describe ashwagandha-related thyrotoxicosis and painless thyroiditis. Those case reports were not in people taking levothyroxine at the same time, so the additive-overreplacement scenario is plausible but not directly documented.
tempeh + levothyroxine
Tempeh is a fermented soybean cake rich in soy protein, and soy protein binds levothyroxine in the gut and reduces how much of the thyroid hormone is absorbed. Fermentation lowers isoflavone bioavailability but leaves the soy protein intact, so the absorption interference remains. Taken consistently close to the dose, this can lower thyroid hormone levels enough to push TSH out of its target range.
edamame + levothyroxine
Edamame is whole young soybeans. Soy protein and isoflavones can bind levothyroxine in the gut and modestly reduce how much is absorbed if the two are taken close together. The evidence is limited and mixed: case reports and one pharmacokinetic study suggest a small reduction in absorption, while the only randomized crossover study found no significant effect. Any impact is best avoided simply by separating the dose from soy-rich meals.
biotin + thyroid stimulating hormone test
High-dose biotin can interfere with the biotin-streptavidin immunoassays many labs use to measure TSH, free T4, free T3, and thyroglobulin. The result is a falsely low TSH alongside falsely elevated free thyroid hormones, a pattern that can mimic Graves' disease. Published case reports describe patients who were wrongly diagnosed with hyperthyroidism, and started on antithyroid drugs, because of biotin interference that resolved once biotin was stopped.
tofu + levothyroxine
Tofu is one of the most concentrated sources of soy protein in the diet. Soy protein binds levothyroxine in the gut and reduces how much of the drug is absorbed, and case reports describe TSH rising when soy-heavy foods like tofu are added to a previously stable levothyroxine regimen. The effect is modest in most adults but clinically relevant in sensitive patients, and it is managed by timing.