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What is levothyroxine sodium, and how does it work? Levothyroxine is a synthetic version of the principal thyroid hormone, thyroxine that is made and released by the thyroid gland. Thyroid hormone increases the metabolic rate of cells of all tissues in the body. In fetus and newborn, thyroid hormones are important for growth and development of all tissues, including bones and the brain. In adults, thyroid hormones help to maintain brain function, utilization of food, and body temperature, among other effects. Generic AVAILABLE: Yes. Generic and branded tablets of levothyroxine may differ: in amount of levothyroxine they contain, absorption of levothyroxine into the body, and distribution of levothyroxine throughout the body. This means that ingestion of 1 mg of GENERIC levothyroxine may not have the same effect on the body as 1 mg of another GENERIC or branded levothyroxine. Practically speaking, this means that when changing between levothyroxine manufactured by different pharmaceutical companies, change in dose may be necessary to maintain the desired effect or to prevent toxicity. When switching between brands or generics, it is important to ensure that both preparations are equivalent or to check blood thyroid levels weekly. For adult hypothyroidism, levothyroxine starts at 12. 5 - 125 mcg / day administered orally. Starting doses and dose changes may differ with individual patients based upon age, presence of cardiovascular disease, development of tolerance, side effects of medication, and blood levels of thyroid hormone. It may take one to three weeks after initiating therapy with levothyroxine or changing dose before effects are see. The goal of replacement therapy is to maintain normal blood thyroxine level. Initiation or discontinuation of therapy with levothyroxine in diabetic patients may create a need for an increase or decrease in the required dose of insulin and / or antidiabetic drug,. Levothyroxine may increase the effect of blood thinners such as warfarin. Therefore, monitoring of blood clotting is necessary, and a decrease in the dose of warfarin may be necessary. Intravenous administration of epinephrine to patients with coronary artery disease may lead to complications ranging from difficulty in breathing to heart attack. These complications may occur more frequently among patients also taking levothyroxine. Therefore, careful observation is needed when intravenous epinephrine is given to patients receiving levothyroxine who also have coronary artery disease. Converting a state of hypothyroidism to a normal state with levothyroxine may decrease actions of certain beta - blocking drugs,. It may be necessary, therefore, to change the dose of beta - blocker. For the same reason, dose of digoxin, drug used to manage heart failure or irregular heart rhythm, also may need to be change. Converting hypothyroidism to euthyroid state with levothyroxine may increase the blood level of theophylline, and it may be necessary to change the dose of theophylline. Taking levothyroxine at the same time as calcium carbonate, ferrous sulfate, cholestyramine or colestipol may decrease the effect of levothyroxine and lead to hypothyroidism. This occurs because levothyroxine binds to these drugs and is not absorb.
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Synthroid is approved to treat hypothyroidism. With this condition, you can have symptoms such as tiredness and weight gain. You may also have muscle weakness and constipation. With hypothyroidism, your body doesnt make enough thyroid hormones. Thyroid hormones are very important to your health because they regulate your metabolism. Your metabolism affects everything from your digestion to your body's growth and repair to even your temperature. The two main Thyroid hormones in your body are called T3 and T4. The Synthroid is a man - made form of T4, and it works by replacing T4 in your body. With Synthroid treatment, your T4 levels increase to a level that is closer to normal. Your body then uses T4 to make T3. Synthroid is approved to treat hypothyroidism that is congenital or acquire. And it approved to treat three main types of hypothyroidism, which are: primary hypothyroidism. With this condition, your Thyroid gland doesnt produce enough Thyroid hormones. Primary hypothyroidism is the most common type of hypothyroidism. It may be caused by an autoimmune disorder called Hashimotos thyroiditis. You may also develop primary hypothyroidism if your thyroid gland has been either treated with radiation or surgically remove. Secondary hypothyroidism. Your pituitary gland is supposed to tell your Thyroid gland to make Thyroid hormones. With secondary hypothyroidism, that doesnt happen. As a result, your Thyroid gland doesnt make enough Thyroid hormones. This condition may be caused by having surgery or radiation on pituitary gland. It may also be caused by trauma to your head that affects your pituitary gland, or pituitary cancer. Tertiary hypothyroidism. Your hypothalamus is supposed to tell your pituitary gland that your body needs more Thyroid hormones. With tertiary hypothyroidism, this doesnt happen. As a result, your pituitary gland doesnt tell your Thyroid gland to make enough Thyroid hormones. Tertiary hypothyroidism may occur if you have cancer in your hypothalamus. Condition can also occur if youve had radiation or surgery on your hypothalamus in the past. These different types of hypothyroidism have different causes. However, synthroid works the same way no matter the cause of condition. There are no statistics to show the effectiveness of Synthroids in treating hypothyroidism. This is because there haven't been any clinical trials that compare Synthroid or products containing Levothyroxine to placebo. This lack of studies is due to drugs age and FDA History of Drug approval requirements. Despite this lack of clinical trials, Levothyroxine is recommended as the primary treatment for hypothyroidism. In 2014, American Thyroid Association released guidelines showing best treatments for hypothyroidism. These guidelines state that products that contain Levothyroxine should be used as standard treatment for hypothyroidism. These guidelines are based on levothyroxine many years of successful use. Years of use have shown that Levothyroxine reduces symptoms of hypothyroidism in most people. Theyve also shown that when people with hypothyroidism stop using Levothyroxine, they begin having symptoms of their condition again. In addition, Levothyroxine treatment has been shown to be safe and without many serious side effects.
Pseudotumor cerebri and slip capital femoral epiphysis have been reported in children receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants and premature closure of epiphyses in children with resultant compromise adult height. Seizures have been reported rarely with institution of levothyroxine therapy. Inadequate levothyroxine dosage will produce or fail to ameliorate signs and symptoms of hypothyroidism. Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products. These include urticaria, pruritus, skin rash, flushing, angioedema, various GI symptoms, fever, arthralgia, serum sickness and wheezing. Hypersensitivity to levothyroxine itself is not known to occur. Read entire FDA prescribing information for Synthroid
Taking levothyroxine with certain drugs may result in an increase in adverse effects. Examples of these drugs include: antidepressants such as amitriptyline and maprotiline. Side effects of both of these antidepressants and levothyroxine may increase when you take these drugs together. This may put you at risk for irregular heart rhythms. Sympathomimetic drugs such as pseudoephedrine and albuterol. The effects of both sympathomimetic drugs and levothyroxine may increase when you take these drugs together. This may put you at risk of serious heart problems. Blood thinners such as warfarin. Taking these drugs with levothyroxine may increase your risk of bleeding. Your doctor may need to decrease the dosage of your blood thinner if you also taking levothyroxine. Ketamine. Taking this drug with levothyroxine may increase your risk of high blood pressure and fast heart rate.
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Fast or irregular heartbeats, chest pain, shortness of breath, fever, hot flashes, sweating, tremors, feeling cold, weakness, tiredness, sleep problems, memory problems, feeling depress, nervous or irritable, headache, leg cramps, muscle aches, dryness of skin or hair, hair loss, changes in your menstrual periods, vomiting, diarrhea, appetite changes, weight changes get medical help right away, if you have any of symptoms list above. Muscle weakness, headache, leg cramps, nervousness, trouble sleeping, diarrhea, skin rash, partial hair loss tell doctor if you have any side effects that bother you or that do not go away. These are not all possible side effects of SYNTHROID. For more information, ask your doctor or pharmacist. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1 - 800 - FDA - 1088. Thyroid hormones, including SYNTHROID, either alone or with other therapeutic agents, should not be used for treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life threatening manifes tations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects.
Fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating;
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Many Drugs affect Thyroid hormone pharmacokinetics and metabolism and may alter therapeutic response to SYNTHROID. In Addition, Thyroid Hormones and Thyroid status have varying effects on pharmacokinetics and actions of other drugs. Listing of Drug - Thyroidal Axis Interactions is contained in Table 2. The List of Drug - Thyroidal Axis Interactions in Table 2 may not be comprehensive due to the introduction of new Drugs that interact with Thyroidal Axis or discovery of previously unknown Interactions. Prescribers should be aware of this fact and should consult appropriate reference sources for additional information if drug - drug interaction with levothyroxine is suspect. Table 2. Drug - Thyroidal Axis Interactions Drugs or Drug Class Effect Drugs that may reduce TSH secretion - reduction are not sustain; therefore, hypothyroidism does not occur. Dopamine / Dopamine Agonists Glucocorticoids Octreotide Use of these Agents may result in transient reduction of TSH secretion when administered at following doses: Dopamine; Glucocorticoids; Octreotide. Drugs that alter Thyroid hormone secretion Drugs that may decrease Thyroid hormone secretion, which may result in hypothyroidism Aminoglutethimide Amiodarone Iodide lithium Methimazole Propylthiouracil sulfonamides Tolbutamide Long - term lithium Therapy can result in goiter in up to 50% of patienradioiodine or surgery are among those individuals who are particularly susceptible to iodine - induced hypothyroidism. Oral cholecystographic Agents and Amiodarone are slowly excrete, producing more prolonged hypothyroidism than parenterally administered iodinate contrast agents. Long - term Aminoglutethimide Therapy may minimally decrease T and T levels and increase TSH, although all values remain within normal limits in most patients. Ts, and either subclinical or overt hypothyroidism, each in up to 20% of patients. Fetus, neonate, elderly and euthyroid patients with underlying thyroid disease e. G, ashimoto's thyroiditis or with Grave's disease previously treated with radioiodine or surgery are among those individuals who are particularly susceptible to iodine - induced hypothyroidism. Oral cholecystographic Agents and Amiodarone are slowly excrete, producing more prolonged hypothyroidism than parenterally administered iodinate contrast agents. Long - term Aminoglutethimide Therapy may minimally decrease T and T levels and increase TSH, although all values remain within normal limits in most patients. Drugs that may increase thyroid hormone secretion, which may result in hyperthyroidism Amiodarone Iodide, including iodine - containing radiographic contrast Agents Iodide and Drugs that contain pharmacologic amounts of Iodide may cause hyperthyroidism in euthyroid patients with Grave's disease previously treated with antithyroid Drugs or in euthyroid patients with Thyroid autonomy e. G, multinodular goiter or hyperfunctioning Thyroid adenoma. Hyperthyroidism may develop over several weeks and may persist for several months after therapy discontinuation. Amiodarone may induce hyperthyroidism by causing thyroiditis. Drugs that may decrease T 4 absorption, which may result in hypothyroidism Antacids - Aluminum & Magnesium Hydroxides - Simethicone Bile Acid Sequestrants - Cholestyramine - Colestipol Calcium Carbonate Cation Exchange Resins - Kayexalate Ferrous Sulfate Orlistat Sucralfate Concurrent Use may reduce efficacy of levothyroxine by binding and delaying or preventing absorption, potentially resulting in hypothyroidism. Calcium Carbonate may form insoluble chelate with levothyroxine, and Ferrous Sulfate likely forms the ferric - thyroxine complex. Administer levothyroxine at least 4 hours apart from these agents. Patients treated concomitantly with Orlistat and levothyroxine should be monitored for changes to thyroid function.
Levothyroxine is used to treat underactive thyroid. It replaces or provides more thyroid hormone, which are normally produced by thyroid gland. Low thyroid hormone levels can occur naturally or when the thyroid gland is injured by radiation / medications or removed by surgery. Having enough thyroid hormone is important for maintaining normal mental and physical activity. In children, having enough thyroid hormones is important for normal mental and physical development. This medication is also used to treat other types of thyroid disorders. This medication should not be used to treat infertility unless it is caused by low thyroid hormone levels. Read Patient Information Leaflet if available from your pharmacist before you start taking levothyroxine and each time you get a refill. If you have any questions, ask your doctor or pharmacist. Take this medication by mouth as directed by your doctor, usually once daily on an empty stomach, 30 minutes to 1 hour before breakfast. Take this medication with a full glass of water unless your doctor directs you otherwise. If you are taking capsule form of this medication, swallow it whole. Do not split, crush, or chew. People who cannot swallow capsules whole should use tablet form of medication. For infants or children who cannot swallow whole tablets, crush the tablet and mix in 1 to 2 teaspoons of water, and give using a spoon or dropper right away. Do not prepare supply in advance or mix tablets in soy infant formula. Consult your pharmacist for more information. Dosage is based on your age, weight, medical condition, laboratory test results, and response to treatment. Use this medication regularly in order to get most benefit from it. To help you remember, take it at same time each day. Do not stop taking this medication without first consulting with your doctor. Thyroid replacement treatment is usually taken for life. There are different brands of levothyroxine available. Do not change brands without first consulting your doctor or pharmacist. Certain medications can decrease the amount of thyroid hormone that is absorbed by your body. If you are taking any of these drugs, separate them from this medication for at least 4 hours. Symptoms of low thyroid hormone levels include tiredness, muscle aches, constipation, dry skin, weight gain, slow heartbeat, or sensitivity to cold. Tell your doctor if your condition worsens or persists after several weeks of taking this medication.
Home PATIENTS Portal CLINICAL THYROIDOLOGY FOR Public Vol 6 Issue 4 Vol 6 Issue 4 p. 4 - 5 CLINICAL THYROIDOLOGY FOR PATIENTS publication OF American THYROID Association summaries FOR PATIENTS From CLINICAL THYROIDOLOGY table OF Contents | PDF File FOR Saving and Printing HYPOTHYROIDISM Generic and brand Levothyroxine preparations ARE not same in children with congenital HYPOTHYROIDISM BACKGROUND HYPOTHYROIDISM is treat by THYROID HORMONE replacement therapy, usually in form OF levothyoxine. There ARE brand Levothyroxine preparations as well as generic preparations. While FDA has deemed generic and branded preparations equal, this has been based on short - term studies in healthy adult volunteers and not long - term treatment OF hypothyroid PATIENTS. In infants with severe congenital HYPOTHYROIDISM, even small changes in THYROID HORMONE levels may have negative effects on their development. Few CLINICAL studies have been performed to date to determine whether generic and brand Levothyroxine preparations ARE truly equal in PATIENTS with HYPOTHYROIDISM. In this STUDY, generic and branded Levothyroxine preparations ARE compared as treatment in a group OF hypothyroid children. Full ARTICLE TITLE: Carswell JM et al. Generic and brand - name L - thyroxine ARE not bioequivalent FOR children with severe congenital HYPOTHYROIDISM. J Clin Endocrinol Metab. December 21, 2012. Summary OF STUDY This STUDY evaluated 31 children and adolescents 3 to 18 years of age with known HYPOTHYROIDISM. A total OF 20 children had congenital HYPOTHYROIDISM, while the rest had Hashimotos thyroiditis as cause of their HYPOTHYROIDISM. Children were assigned to receive their usual Levothyroxine dose as either Synthroid TM or Generic Levothyroxine FOR 8 weeks and then were switched to other preparation FOR 8 weeks. Serum TSH, free T 4, and total T 3 were measured at the end of each 8 week treatment period and were compared FOR each subject. Serum TSH was significantly lower after 8 weeks OF SynthroidTM than after 8 weeks OF Generic Levothyroxine. This difference does not depend on age and was seen only in children with congenital HYPOTHYROIDISM. In children with Hashimotos Disease, TSH does not differ between branded and generic Levothyroxine. There were no differences in free T 4 or total T 3 following each treatment period. What ARE the IMPLICATIONS OF this STUDY? This STUDY demonstrates that Synthroid and Generic Levothyroxine ARE not equal in children with congenital HYPOTHYROIDISM, even though the FDA States they ARE interchangeable. This difference was not observed in PATIENTS with Hashimotos thyroiditis, possibly because they have intact THYROID although it is not working. Results in children with congenital HYPOTHYROIDISM may possibly be seen in other PATIENTS who have had thyroidectomy. In any event, this STUDY reinforces the need to check THYROID tests to adjust dose when Levothyroxine preparations ARE being change. Further studies with a larger number of PATIENTS would be helpful to confirm these results. Table OF Contents | PDF File FOR Saving and Printing Hashimotos thyroiditis: most common cause OF HYPOTHYROIDISM in the United States. It is caused by antibodies that attack THYROID and destroy gland.
To determine the right dosage of levothyroxine initially, your doctor generally checks your level of TSH after six to eight weeks of treatment and again after any dose changes. Once the dose that normalizes your thyroid tests is determined, your doctor is likely to check your TSH level about every 12 months as the dosage you need may change. Excessive amounts of thyroid hormone can accelerate bone loss, which may make osteoporosis worse or add to your risk of this disease. Overtreatment with levothyroxine can also cause heart rhythm disorders. 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 drug. If you do, signs and symptoms will gradually return.
What are Thyroid replacement hormones and how do they work? Thyroid replacement hormones are medications used to treat hypothyroidism, condition in which production of Thyroid hormones in the body is abnormally low. Thyroid hormones increase cellular metabolism that is responsible for growth, development of tissues, maintenance of brain function, body temperature regulation and several other cellular processes. Low levels of Thyroid hormones in the body can result in many problems give numerous activities that they mediate. The thyroid gland, gland found in the lower neck, is responsible for production of thyroid hormones. It produces two main hormones, thyroxine and triiodothyronine. The hormone responsible for most biological effects in the body is T3. When T4 is released into the blood by Thyroid gland, most of it is converted to T3, which is responsible for cellular metabolic processes. Commercially available Thyroid hormones are either natural or synthetic. Desiccate Thyroid or Thyroid extract, natural Thyroid hormone is derived from beef or pork. Levothyroxine Sodium, is a synthetic version of thyroxine, liothyronine Sodium, is a synthetic version of tT3 and liotrix is a synthetic Thyroid hormone containing a mixture of T4and T3. Thyroid replacement hormones are used to treat hypothyroidism and myxedema, condition that is caused by prolonged hypothyroidism. Thyroid replacement hormones prevent Thyroid hormone release from cancerous Thyroid nodules and are used therefore to treat Thyroid cancers. They are also used to manage thyrotoxicosis, condition in which there are high levels of Thyroid hormones resulting from over - active Thyroid glands and too much Thyroid hormone. Thyrotoxicosis may progress to hypothyroidism or cause growth of goiters necessitating use of Thyroid replacement hormones. Are there any differences between different types of Thyroid replacement hormones? There is conflicting evidence regarding which hormone replacement therapy should be prefer. The American Association of Clinical Endocrinologists recommends that clinical hypothyroidism is best treated with synthetic T4 Levothyroxine. There is variability between absorption and distribution of generic T4 compared to brand - name preparations. Hence, it is recommended that patients remain with specific brand names during treatment. There is also variability between generic formulations and brand names of pure T3, combined T4 / T3 formulations and Thyroid extracts from animal sources. Thyroid extracts from animal sources are no longer available in the United States. Emerging information shows that the combination of T4 / T3 therapy may have some advantages over T4 in cognitive performance and mood, but studies are not conclusive. Thyroid replacement hormones are usually well tolerate. Symptoms that occur during treatment are often due to toxic, elevated levels of Thyroid hormones and resulting symptoms of hyperthyroidism. Symptoms may include chest pain, increased heart rate or pulse rate, excessive sweating, heat intolerance, nervousness, headache, insomnia, diarrhea, vomiting, weight loss, and fever. Some women may experience irregular menstrual cycles.
The primary treatment for most thyroid cancers is surgery with removal of the entire Thyroid gland or lobe of Thyroid gland. After surgery, patients will require Thyroid hormone replacement medication to replace Thyroid hormone production and suppress tumor regrowth. Levothyroxine is used to treat hypothyroidism due to Thyroid surgery for cancer just as it is used for other cases of underactive Thyroid. Depending on the extent of disease and the person's risk for recurrent Thyroid cancer, doctor will determine what range TSH should be suppressed to and adjust levothyroxine accordingly. For large Thyroid cancers, Thyroid cancer that has spread to lymph nodes, and / or if you are considered high risk for recurrent cancer, radioiodine therapy may be given after surgery. Radioactive iodine is given is given in hospital settings in either liquid form or as a capsule. Its main goal is to kill off cancer cells that remain after surgery and destroy any remaining Thyroid tissue. Chemotherapy, which works by killing rapidly dividing cells, like cancer cells, is not often used to treat thyroid cancer unless a person has recurrent and / or metastatic cancer. Chemotherapy is also combined with external beam radiation for treatment of a rare type of Thyroid cancer called anaplastic Thyroid cancer. Scientists have developed several drugs called targeted therapies that target specific markers on cancer cells. Some of these drugs have been used to treat advanced or resistant Thyroid cancer. Nexavar and Lenvima are two targeted therapies kinase inhibitors that work partially by blocking Thyroid cancers from growing and making new blood vessels.
|Hormone||Ratio in Thyroglobulin||Biologic Potency||t 1/2 (days)||Protein Binding (%) a|
|Levothyroxine (T4)||10 - 20||1||6-7 b||99.96|
Despite this, there are some individuals for whom generic Levothyroxine may not be advise. In particular: those who have had thyroid cancer: Fluctuating TSH, which can occur from inconsistent thyroid hormone replacement, can affect the body's ability to prevent cancer from returning. Discuss treatment options with your doctor. Those with certain allergies, digestive conditions, or who have drug absorption issues: in these cases, Tirosint softgel option that only contains Levothyroxine, gelatin, glycerin, and watermay be specifically recommend. It's important to note, however, that this drug is costly and not widely prescribe. It may not be covered by your insurance company at all or without explanation of need from your doctor. If these situations don't apply to you and you decide that changing to generic is the way to go for cost - saving reasons, be sure to speak with your doctor about the recommended schedule for checking your TSH levels. Getting several - month supply: When you fill prescription written to last you for several months, you 'll ensure that you are taking medication with the same potency and ingredients for that duration. Talk To Your pharmacist: Once you learn that you re stable on a particular generic, ask the pharmacist if it's possible to get refills from that same manufacturer. This may not always be possible, but it is worth ask.
|AGE||Daily Dose Per Kg Body Weight a|
|0-3 months||10-15 mcg/kg/day|
|3-6 months||8-10 mcg/kg/day|
|6-12 months||6-8 mcg/kg/day|
|1-5 years||5-6 mcg/kg/day|
|6-12 years||4-5 mcg/kg/day|
|Greater than 12 years but growth and puberty incomplete||2-3 mcg/kg/day|
|Growth and puberty complete||1.6 mcg/kg/day|
|Strength (mcg)||Color additive(s)|
|25||FDC Yellow No. 6 Aluminum Lake a|
|75||FDC Red No. 40 Aluminum Lake, FDC Blue No. 2 Aluminum Lake|
|88||FDC Blue No. 1 Aluminum Lake, FDC Yellow No. 6 Aluminum Lake a , DC Yellow No. 10 Aluminum Lake|
|100||DC Yellow No. 10 Aluminum Lake, FDC Yellow No. 6 Aluminum Lake a|
|112||DC Red No. 27 30 Aluminum Lake|
|125||FDC Yellow No. 6 Aluminum Lake a , FDC Red No. 40 Aluminum Lake, FDC Blue No. 1 Aluminum Lake|
|137||FDC Blue No. 1 Aluminum Lake|
|150||FDC Blue No. 2 Aluminum Lake|
|175||FDC Blue No. 1 Aluminum Lake, DC Red No. 27 30 Aluminum Lake|
|200||FDC Red No. 40 Aluminum Lake|
|300||DC Yellow No. 10 Aluminum Lake, FDC Yellow No. 6 Aluminum Lake a , FDC Blue No. 1 Aluminum Lake|
Usually, if youre already taking Synthroid, youll continue taking it during pregnancy. Some information shows that taking Synthroid during pregnancy doesnt increase the risk of birth defects or pregnancy loss. In fact, hypothyroidism, which Synthroid is used to treat, can actually be dangerous during pregnancy. Not having enough thyroid hormone in your body, which happens in hypothyroidism, can increase certain risks. These risks include pregnancy loss, high blood pressure during pregnancy, and premature delivery. If you have a thyroid condition, it is important that your doctor monitors your thyroid while youre pregnant. In some cases, pregnancy may increase your thyroid hormone needs. In that case, you need to take more Synthroid than you did before pregnancy. If needed during your pregnancy, your doctor will increase your dosage of Synthroid. If youre pregnant or planning to become pregnant, talk to your doctor about how to manage Synthroid treatment.
Synthroid and levothyroxine are both approved for TSH suppression and to treat hypothyroidism. Use of Synthroid and levothyroxine in treating hypothyroidism has been directly compared in clinical study. This study, done in 1997, looked at people taking either Synthroid or levothyroxine. It show that there was no significant difference in thyroid hormone levels between the two groups of people. But studies comparing Synthroid with levothyroxine have also shown mixed results. For example, in one study of children, Synthroid lowers people's TSH levels more than levothyroxine does. But in different studies of children, levothyroxine lowers people's TSH level more than Synthroid does. Tsh levels indicate how much your body needs Thyroid hormone. Lower TSH levels mean that Thyroid hormone is being adequately replaced with treatment. In both of these studies, Synthroid and levothyroxine were effective in treating people's hypothyroidism. However, mixed study results do support the recommendation that you shouldnt switch back and forth between brand - name Synthroid and generic levothyroxine. For more information about switching between these drugs, see Synthroid generic section above.
Synthroid and Armour Thyroid both contain medications used for Thyroid conditions. Therefore, these medications can cause very similar side effects, but some different ones as well. Below are examples of these side effects. It is important to note that most of the side effects of both Synthroid and Armour Thyroid are due to having too many Thyroid hormones in your body. Even small changes in your doses of these drugs may cause large changes in your hormone levels, which may result in side effects. Be sure to talk with your doctor about any side effects you have with these drugs. In some cases, your doctor may need to adjust your dosage of drug.
Thyroid hormone synthesis and secretion is regulated by the hypothalamic - pituitary - thyroid axis. Thyrotropin - releasing hormone release from the hypothalamus stimulates secretion of thyrotropin - stimulating hormone, TSH, from the anterior pituitary. Tsh, in turn, is physiologic stimulus for synthesis and secretion of thyroid hormones, L - thyroxine and L - triiodothyronine, by thyroid gland. Circulating serum T 3 and T 4 levels exert feedback effect on both TRH and TSH secretion. When serum T 3 and T 4 levels increase, TRH and TSH secretion decrease. When thyroid hormone levels decrease, TRH and TSH secretion increase. Mechanisms by which thyroid hormones exert their physiologic actions are not completely understood, but it is thought that their principal effects are exerted through control of DNA transcription and protein synthesis. T 3 and T 4 diffuse into cell nucleus and bind to thyroid receptor proteins that attach to DNA. This hormone nuclear receptor complex activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins. Thyroid hormones regulate multiple metabolic processes and play an essential role in normal growth and development, and normal maturation of the central nervous system and bone. Metabolic actions of thyroid hormones include augmentation of cellular respiration and thermogenesis, as well as metabolism of proteins, carbohydrates and lipids. Protein anabolic effects of thyroid hormones are essential to normal growth and development. Physiological actions of thyroid hormones are produced predominantly by T 3, majority of which is derived from T 4 by deiodination in peripheral tissues. Levothyroxine, at doses individualized according to patient response, is effective as replacement or supplemental therapy in hypothyroidism of any etiology, except transient hypothyroidism during recovery phase of subacute thyroiditis. Levothyroxine is also effective in suppression of pituitary TSH secretion in treatment or prevention of various types of euthyroid goiters, including thyroid nodules, Hashimoto's thyroiditis, multinodular goiter AND, as adjunctive therapy in management of thyrotropin - dependent welldifferentiated thyroid cancer.
Experience with levothyroxine use in pregnant women, including data from post - marketing studies, has not reported increased rates of major birth defects or miscarriages; there are risks to mother and fetus associated with untreated hypothyroidism in pregnancy; since TSH levels may increase during pregnancy, TSH should be monitored and levothyroxine dosage adjust during pregnancy; untreated maternal hypothyroidism may have adverse effect on fetal neurocognitive development maternal hypothyroidism during pregnancy is associate with higher rate of complications, including spontaneous abortion, gestational hypertension, pre - eclampsia, stillbirth, and premature delivery; untreated maternal hypothyroidism may have adverse effect on fetal neurocognitive development pregnancy may increase thyroid hormone requirements. Serum TSH level should be monitored and dosage adjusted during pregnancy; since postpartum TSH levels are similar to preconception values, dosage should return to pre - pregnancy dose immediately after delivery.
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