thyroglobulin ( tg ) is the protein that serves as the precursor molecular for thyroid hormones.
thyroglobulin ( tg ) is the protein that serves as the precursor molecular for thyroid hormones.
protein that serves as the precursor molecular for thyroid hormones?
thyroglobulin ( tg )
thyroglobulin (tg) is a 660 kda, dimeric protein produced by the follicular cells of the thyroid and used entirely within the thyroid gland. thyroxine is produced by attaching iodine atoms to the ring structures of this protein's tyrosine residues; thyroxine (t) contains four iodine atoms, while triiodothyronine (t), otherwise identical to t, has one less iodine atom per molecule. the thyroglobulin protein accounts for approximately half of the protein content of the thyroid gland. each thyroglobulin molecule contains approximately 100-120 tyrosine residues, a small number of which (<20) are subject to iodination catalysed by thyroperoxidase. the same enzyme then catalyses "coupling" of one modified tyrosine with another, via a free radical-mediated reaction, and when these iodinated bicyclic molecules are released by hydrolysis of the protein, t3 and t4 are the result. therefore, each thyroglobulin protein molecule ultimately yields very small amounts of thyroid hormone (experimentally observed to be on the order of 5-6 molecules of either t4 or t3 per original molecule of thyroglobulin).
thyroid hormones
most people are treated with levothyroxine, or a similar synthetic thyroid hormone. different polymorphs of the compound have different solubilities and potencies. additionally, natural thyroid hormone supplements from the dried thyroids of animals are still available. levothyroxine contains t4 only and is therefore largely ineffective for patients unable to convert t4 to t3. these patients may choose to take natural thyroid hormone, as it contains a mixture of t4 and t3, or alternatively supplement with a synthetic t3 treatment. in these cases, synthetic liothyronine is preferred due to the potential differences between the natural thyroid products. some studies show that the mixed therapy is beneficial to all patients, but the addition of lyothyronine contains additional side effects and the medication should be evaluated on an individual basis. some natural thyroid hormone brands are fda approved, but some are not. thyroid hormones are generally well tolerated. thyroid hormones are usually not dangerous for pregnant women or nursing mothers, but should be given under a doctor's supervision. in fact, if a woman who is hypothyroid is left untreated, her baby is at a higher risk for birth defects. when pregnant, a woman with a low-functioning thyroid will also need to increase her dosage of thyroid hormone. one exception is that thyroid hormones may aggravate heart conditions, especially in older patients; therefore, doctors may start these patients on a lower dose and work up to a larger one to avoid risk of heart attack.
thyroid hormones