Thyroid peroxidase activity is inhibited by amino acids

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“Muscle catabolism also releases a large amount of cysteine, and cysteine, methionine, and tryptophan suppress thyroid function (Carvalho, et al., 2000).” -Ray Peat, PhD

“Muscle protein is very rich in tryptophan and cysteine, and these amino acids suppress the thyroid gland’s function, and are potentially toxic to nerves, especially in the presence of cortisol and hypoglycemia. Tryptophan is turned into serotonin, which promotes lipid peroxidation, blood clotting, and certain patterns of nerve activity. Serotonin can suppress mitochondrial respiration, and along with the reduced body temperature that it produces, a pattern or torpor or helplessness tends to be produced.” -Ray Peat, PhD

“The selection of amino proteins should minimize the amino acids tryptophan (which is the precursor to serotonin) and cysteine (which like tryptophan, suppresses thyroid function), by including gelatin and fruits. Gelatin is 22% glycine, which protects the lungs and other organs against toxins and inflammatory agents, and many fruits are also “deficient” in tryptophan and cysteine.” -Ray Peat, PhD

Braz J Med Biol Res. 2000 Mar;33(3):355-61.
Thyroid peroxidase activity is inhibited by amino acids.
Carvalho DP, Ferreira AC, Coelho SM, Moraes JM, Camacho MA, Rosenthal D.
Normal in vitro thyroid peroxidase (TPO) iodide oxidation activity was completely inhibited by a hydrolyzed TPO preparation (0.15 mg/ml) or hydrolyzed bovine serum albumin (BSA, 0.2 mg/ml). A pancreatic hydrolysate of casein (trypticase peptone, 0.1 mg/ml) and some amino acids (cysteine, tryptophan and methionine, 50 microM each) also inhibited the TPO iodide oxidation reaction completely, whereas casamino acids (0.1 mg/ml), and tyrosine, phenylalanine and histidine (50 microM each) inhibited the TPO reaction by 54% or less. A pancreatic digest of gelatin (0.1 mg/ml) or any other amino acid (50 microM) tested did not significantly decrease TPO activity. The amino acids that impair iodide oxidation also inhibit the TPO albumin iodination activity. The inhibitory amino acids contain side chains with either sulfur atoms (cysteine and methionine) or aromatic rings (tyrosine, tryptophan, histidine and phenylalanine). Among the amino acids tested, only cysteine affected the TPO guaiacol oxidation reaction, producing a transient inhibition at 25 or 50 microM. The iodide oxidation inhibitory activity of cysteine, methionine and tryptophan was reversed by increasing iodide concentrations from 12 to 18 mM, while no such effect was observed when the cofactor (H2O2) concentration was increased. The inhibitory substances might interfere with the enzyme activity by competing with its normal substrates for their binding sites, binding to the free substrates or reducing their oxidized form.

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4 Responses

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  1. dadon says

    What biological function could that have?

  2. Team FPS says

    Possible protective slowing of the metabolism to retard the consumption of tissues during stress.

  3. Christy Fox says

    I have come upon this article which intrigues me b/c I’ve been working on lowering my thyroid TPO for several years. I’ve been gluten free, egg free, dairy free, and most recently grain & nut free. Could you possibly tell me in laymen’s terms what you’re suggesting in this article? Perhaps, I should try gelatin as a dietary supplement? I do some homemade bone broth, but more in the cold months. I greatly appreciate any insight you’re willing to give. My Naturopathic doc & I would really like to see the TPO drop!

  4. Team FPS says

    The TPO on your test is a TPO antibodies test that doctors use as marker for autoimmune susceptibility of the thyroid gland. This blog suggests that the amino acids cysteine, methionine, and tryptophan inhibit thyroid peroxidase (TPO) enzyme that helps form thyroid hormone in the gland. The test isn’t measuring what this blog is discussing directly.

    I see a high TPO antibodies result as a indicator of stress to the thyroid gland. Usually polyunsaturated fats (PUFA) both eaten currently and stored in the tissues alone with estrogen are big players in stressing the gland. Both PUFA and estrogen tend to promote each other in a viscous cycle.

    Estrogen and Autoimmune Connection

    Saturated fats like coconut oil; sugar from ripe fruits, milk, and orange juice; gelatin from broth or as supplement from great lakes gelatin; and supplemental progesterone are things to discuss with your doctor to help relieve the stress on the gland. A raw carrot daily or bamboo shoots can manipulate the gut flora positively and reduce the likelihood of a high test result. Since antibodies can take months to lower, you will need to be patient while implementing new strategies.

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