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Levothyroxine Vs Synthroid

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Last Updated: 16 September 2020

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General | Latest Info

Hypothyroidism has been estimated to affect > 10 million Americans over the age of 12 years. Although the condition is less common in young, people infants and children comprise a particularly vulnerable population because of the critical role of Thyroid hormone in growth and brain development. Like in adult hypothyroid patients in whom even minor deviations in Thyroid hormone equilibrium have been associated with adverse effects on a variety of target organs, including bone, lipids, heart and neurocognition, precise titration of Levothyroxine replacement is important in infants and children. For example, in babies with severe congenital hypothyroidism, increase in recommended starting L - T 4 dose from 6 - 8 g / kg / d to 10 - 15 g / kg / d has been associated with significant improvement in cognitive outcome, and even mild maternal Thyroid dysfunction during pregnancy has been related to decrement in intellectual and motor development of offspring. As a result, in clinical practice, often dose is adjusted by increments of 10% or less to keep serum TSH concentration within the therapeutic range. In the United States, multiple brand and GENERIC formulations of L - T 4 are AVAILABLE for use, and whether or not they can be substituted without retitration is a matter of great controversy. The Federal Drug Administration determines bioequivalence on the basis of pharmacokinetic parameters in euthyroid adult volunteers who are administered supraphysiological dose of test L - T 4 formulation. Results are compared with 1 of 4 reference preparations. If 90% confidence interval of difference in area under curve and maximum T 4 concentration falls between 80% and 125% of reference formulation, products are considered to be Bioequivalent and therefore therapeutically equivalent and interchangeable. Although this pharmacokinetic paradigm may be appropriate for comparing formulations of many classes of drugs, large body of evidence suggests that it is too insensitive to assess therapeutic equivalence for L - T 4 because it ignores effects on serum TSH concentration and contribution of endogenous T 4 production. The relation between serum concentration of T 4 and TSH is log - linear such that small changes in serum free T 4 concentration result in much larger changes in TSH level, and in hypothyroid adults, administration of just 25 g L - T 4 less than optimal results in significant elevation in serum TSH concentration in most subjects but no change in either circulating free T 4 or free T 3 level. Similarly, in a pharmacokinetic study of 36 normal volunteers, Blakesley et al have demonstrated that when current FDA methodology is used and no baseline correction is made for endogenous T 4 pool, differences as large as 25% - 33% of administered dose would not be detect, and even after baseline correction, difference of 12. 5% would not be identify.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Levothyroxine Preparations

Synthroid may interact with ferrous sulfate iron supplements, sucralfate, and antacids. Synthroid may also interact with dopamine / dopamine agonists, glucocorticoids, octreotide, aminoglutethimide, amiodarone, iodide, lithium, methimazole, propylthiouracil, sulfonamides, tolbutamide, orlistat, clofibrate, oral contraceptives, estrogens, heroin / methadone, 5 - fluorouracil, mitotane, tamoxifen, furosemide, heparin, hydantoins, nonsteroidal anti - inflammatory drugs, salicylates, carbamazepine, phenobarbital, rifampin, beta - adrenergic antagonists, anticoagulants, antidepressants, antidiabetics, cardiac glycosides, cytokines, growth hormones, ketamine, bronchodilators, radiographic agents, sympathomimetics, chloral hydrate, diazepam, ethionamide, lovastatin, metoclopramide, 6 - mercaptopurine, nitroprusside, para - aminosalicylate sodium, perphenazine, resorcinol, and thiazide diuretics. Levothroid may interact with ferrous sulfate iron supplements, sucralfate, and antacids. Levothroid may also interact with calcium carbonate, sodium polystyrene sulfonate, and cholesterol - lowering drugs. Synthroid is prescribed in tablets that range from 25 to 300 mcg in strength and is usually taken once a day with a full glass of water 30 to 60 minutes before breakfast for best adsorption into body. Children can take medicine if a tablet is crushed and put into about 1 to 2 teaspoons of water; do not store or delay giving this crush pill suspension. Doctors often have to slowly increase the dose; Patients should not increase or decrease this medication themselves. Because some preparations of Drug may contain iodine or lactose, patients should tell their doctors about such allergies or reactions to these components. Many drugs can inhibit Synthroid's adsorption by body; other medications may increase or decrease its effectiveness once it is adsorb. Providing a complete list of medications to doctor will help with getting the correct dose established for each individual patient. Pregnant and lactating females need to discuss dose and use of this medication with their caregivers. For adult hypothyroidism, Levothroid starts at 12. 5 - 125 mcg / day take orally. Dose may differ with individuals based on age, presence of cardiovascular disease, tolerance, side effects, and blood levels of Thyroid hormone. It may take one to three weeks before effects are see.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Special Considerations

Levothyroxine should not be used alone or along with other treatments to treat obesity or cause weight loss. Levothyroxine may cause serious or life - threatening problems when given in large doses, especially when taken with amphetamines such as amphetamine, dextroamphetamine, and methamphetamine. Tell your doctor if you have any of the following symptoms while you are taking levothyroxine: chest pain, rapid or irregular heartbeat or pulse, uncontrollable shaking of part of your body, nervousness, anxiety, irritability, difficulty falling asleep or staying asleep, shortness of breath, or excessive sweating. Talk to your doctor about potential risks associated with this medication. Levothyroxine is used to treat hypothyroidism. It is also used with surgery and radioactive iodine therapy to treat Thyroid cancer. Levothyroxine is in a class of medications called hormones. It works by replacing Thyroid hormone that is normally produced by the body. Without Thyroid hormone, your body cannot function properly, which may result in poor growth, slow speech, lack of energy, excessive tiredness, constipation, weight gain, hair loss, dry, thick skin, increased sensitivity to cold, joint and muscle pain, heavy or irregular menstrual periods, and depression. When taken correctly, levothyroxine reverses these symptoms. Levothyroxine comes as a tablet and capsule to take by mouth. It usually takes one day on an empty stomach, 30 minutes to 1 hour before breakfast. Follow directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take levothyroxine exactly as direct. Do not take more or less of it or take it more often than prescribed by your doctor. Swallow capsules whole; do not chew or crush them. Do not remove the capsule from the package until you are ready to take it. Take tablets with a full glass of water as they may get stuck in your throat or cause choking or gagging. If you are giving levothyroxine to an infant, child, or adult who cannot swallow tablet,ss crush and mix it in 1 to 2 teaspoons of water. Only mix crush tablets with water; do not mix them with food or soybean infant formula. Give this mixture by spoon or dropper right away. Do not store it for later use. Your doctor will probably start you on a low dose of levothyroxine and gradually increase your dose. Levothyroxine controls hypothyroidism but does not cure it. It may take several weeks before you notice a change in your symptoms. Continue to take levothyroxine even if you feel well. Do not stop taking levothyroxine without talking to your doctor.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

USE

The average replacement dose of T4 in adults is approximately 1. 6 mcg / kg per day, which would be 112 mcg per day in a 70 - kg adult, but this is not a one - size - fit - all recommendation. Synthroids should be taken on an empty stomach, ideally hour before breakfast. Another option is to take it at bedtime if youve had nothing to eat for several hours. High - fiber diets, coffee, and iron and calcium supplements can interfere with levothyroxine absorption by up to 30%. Be careful if you take other medications. People on estrogen therapy may need to up their levothyroxine dosage. And proton pump inhibitors like omeprazole and Nexium can limit levothyroxine absorption.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Discussion

Up to 7% of the general population has hypothyroidism, which is corrected with Thyroid hormone treatment. General goals of Thyroid hormone replacement are to provide resolution of patient symptoms and hypothyroid signs, including biological and physiologic markers of hypothyroidism; achieve normalization of serum Thyroid - stimulating hormone concentrations with improvement in circulating Thyroid hormone concentrations; and avoid overtreatment, especially in elderly persons. Levothyroxine, synthetically made thyroxine, is the predominant form of Thyroid hormone replacement used for patients with hypothyroidism. Let's discuss important issues surrounding use of levothyroxinewhat are expected benefits, and why do some people supplement with therapies containing T3?

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

What is Synthroid?

With hypothyroidism, your body isnt making enough thyroid hormones. These hormones are very important because they affect your metabolism. Synthroid increases your body's thyroid hormone levels back to normal range. Synthroid is approved to treat three main types of hypothyroidism: primary secondary tertiary. Synthroid is approved to treat hypothyroidism that is congenital or acquire. For more detail on hypothyroidism, see Synthroid uses section below.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Hashimoto's Thyroiditis

What are your feeling regarding natural vs. Synthetic replacement therapy in hypothyroid situations? Armour, for example, vs. Synthroid? My daughter is exceedingly sensitive to most medications and is in the process of being diagnosed with possible Hashimoto's. While it is reasonable to assume that synthetic medications are less desirable than natural counterparts, in this case - natural Thyroid hormone replacement is definitely not the ideal solution for the vast majority of people. Armour Thyroid is derived from desiccated pig Thyroid gland. A number of years ago, these natural preparations were our only alternative. Replacement with desiccated Thyroid creates dosing problems because there is no way to standardize the exact amount of dose for each batch. As a matter of fact, these preparations do not report their dosage strength in milligrams, but rather, in grains of Thyroid. This is because, they don't really know the milligram equivalent in each dose. Dosing is also based on assumptions that each gland has equal amounts of hormones as next gland, and that the ratio of T4 and T3 is similar and constant in each gland from pigs. There is no way to be certain of this, and patients on these preparations often have fluctuating hormone levels, which may or may not result in symptoms. Regardless of symptoms, goal of replacement therapy is to keep hormone levels as stable as possible. This is much easier to achieve with synthetic preparations such as Levoxyl and Synthroid. These preparations come in vast number of standardized doses, allowing for minute adjustments in hormone dosing. There is another comment that should be make. With all issues surrounding mad cow disease and other ailments, I personally am reluctant to offer animal base therapy to patients when safe, effective well - studied synthetic preparation is widely available. I hope this helps answer any questions you may have.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

TSH blood tests

Proper interpretation of thyroid function tests requires understanding of thyroid physiology. Thyroid function is regulated by a relatively straightforward relationship between the hypothalamus, pituitary, and thyroid gland itself. Thyrotropin releasing hormones from the hypothalamus stimulates release of TSH from the pituitary gland which, in turn, regulates a variety of steps in production of thyroid hormones from uptake of iodine to regulation of enzymatic steps in the process. The majority of thyroid hormone released by the gland is thyroxine, while a smaller proportion is tri - iodothyronine. These thyroid hormones are highly protein - bound, with only free components having the ability to bind to their respective receptors. Active thyroid hormone is free T3, and there is tissue - specific regulation of conversion of T4 to T3 by a set of deiodinase enzymes peripherally, allowing each tissue to, in a sense, self - regulate its exposure to free T3. This is crucial, because different tissues require different levels of T3. This conversion of T4 to T3 is how treatment of hypothyroidism with levothyroxine still allows for adequate, tissue - specific, T3 exposure. Next, it is essential to appreciate negative feedback of free T3 and free T4 at level of hypothalamus and pituitary. Also, relationship between these thyroid hormones and TSH is not linear but log - linear, such that very small changes in free T3 and / or free T4 will result in very large changes in TSH. Conversely, very small changes in TSH reflect extremely minute changes in free T3 and free T4. For instance, 2 - fold change in free T4 will result in a 100 - fold change in TSH. Thus, free T4 change from 1. 0 ng / dL to 0. 5 ng / dL will result in TSH rise from 0. 5 mIU / mL to 50 mIU / mL. On other hand, rise in TSH from 1. 0 mIU / mL to 5. 0 mIU / mL reflects drop in free T4 from 1. 0 ng / dL to just 0. 9 ng / dL. It is also important to note that each individual has a set point for their own free T3 and free T4 level that is quite stable in the absence of disease. Therefore, changes in any give patients free T3 and / or free T4 within normal range will result in abnormal TSH value. This supports the role of TSH, in the absence of hypothalamic / pituitary disease, as the most sensitive marker of thyroid function. Table 1 lists common patterns of thyroid function tests and their interpretation, assuming intact hypothalamic - pituitary - thyroid axis and absence of significant non - thyroidal illness. These interpretations will be valid in the vast majority of non - hospitalized patients presenting to primary care provider.Ss


Treatment

To determine the right dosage of levothyroxine initially, your doctor generally checks your level of TSH after six to eight weeks. After that, blood levels are generally checked six months later. Excessive amounts of hormones can cause side effects, such as: increased appetite, Insomnia, Heart palpitations Shakiness If you have coronary artery disease or severe hypothyroidism, your doctor may start treatment with a smaller amount of medication and gradually increase the dosage. Progressive hormone replacement allows your heart to adjust to an increase in metabolism. Levothyroxine causes virtually no side effects when used at an appropriate dose and is relatively inexpensive. If you change brands, let your doctor know to ensure you re still receiving the right dosage. Also, don't skip doses or stop taking drugs because you re feeling better. If you do, symptoms of hypothyroidism will gradually return.


What is thyroid hormone?

Thyroid Hormone Treatment Levothyroxine is standard of care in thyroid Hormone replacement therapy and treatment of hypothyroidism. Levothyroxine is equivalent to the T4 form of naturally occurring thyroid Hormone and is available in generic and brand - name forms. How do I take Levothyroxine? To optimize absorption of your thyroid medication, it should be taken with water at regular time each day. Multiple medications and supplements decrease absorption of thyroid Hormone and should be taken 3 - 4 hours apart, including calcium and iron supplements, proton pump inhibitors, soy, and multivitamins with minerals. Because of the way Levothyroxine is metabolized by the body, your doctor may ask you to take extra pills or skip pills on some days of the week. This helps us to fine tune your medication dose for your body and should be guided by an endocrinologist. For patients with celiac disease or gluten sensitivity, gluten free formulation of Levothyroxine is available. Some individuals may have genetic variants that affect how the body converts T4 to T3 and these individuals may benefit from the addition of a small dose of triiodothyronine. Liothyronine is a replacement T3 thyroid Hormone. This medication has a short half - life and is taken twice per day or in combination with Levothyroxine. Liothyronine alone is not used for treatment of hypothyroidism long term. Other formulations of thyroid hormone replacement include natural or desiccated thyroid hormone extracted from animal sources. Natural or desiccated thyroid extract preparations have greater variability in dose of thyroid Hormone between batches and imbalanced ratios if T4 vs T3. Natural or animal sources of thyroid hormone typically contain 75% T4 and 25% T3, compared to the normal human balance of 95% T4 and 5% T3. Treatment with a correct balance of T4 and T3 is important to replicate normal thyroid function and prevent adverse effects of excess T3, including osteoporosis, heart problems, and mood and sleep disturbance. An endocrinologist can evaluate symptoms and thyroid tests to help balance thyroid hormone medications.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Sources

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

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