Understanding Possible Side Effects

Thyroid hormones, including SYNTHROID, either alone or with other therapeutic agents, should not be used for the 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 manifestationsof toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects. Circulating thyroid hormones are greater than 99% bound to plasma proteins, including thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin (TBA), whose capacities and affinities vary for each hormone. The higher affinity of both TBG and TBPA for T4 partially explains the higher serum levels, slower metabolic clearance, and longer half-life of T4 compared to T3. Protein-bound thyroid hormones exist in reverse equilibrium with small amounts of free hormone.

Reading on Thyroid health

Carefully monitor glycemic control after starting, changing, or discontinuing SYNTHROID see DRUG INTERACTIONS. For secondary or tertiary hypothyroidism, serum TSH is not a reliable measure of SYNTHROID dosage adequacy and should not be used to monitor therapy. Use the serum free-T4 level to titrate SYNTHROID dosing until the patient is clinically euthyroid and the serum free-T4 level is restored to the upper half of the normal range see Recommended Dosage And Titration. A case control study on 15 SCH and 15 euthyroid controls revealed significantly lower FVIII and vWF activities in SCH compared to controls, which is in favor of a bleeding tendency. However, bleeding time and PT were similar between SCH and controls (38). Fibrinogen and PAI-1 levels are significantly lower in hypothyroid patients compared to their euthyroid state after hormone replacement therapy (48).

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Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and SYNTHROID may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. Toxic effects may include increased risk of cardiac arrhythmias and central nervous system stimulation. Administration of sertraline in patients stabilized on SYNTHROID may result in increased SYNTHROID requirements. Addition of SYNTHROID therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements. Carefully monitor glycemic control, especially when thyroid therapy is started, changed, or discontinued see WARNINGS AND PRECAUTIONS.

• Treat patients with adrenal insufficiency with replacement glucocorticoids prior to initiating treatment with SYNTHROID see CONTRAINDICATIONS.
• Thyroid hormones exert their physiologic actions through control of DNA transcription and protein synthesis.
• In summary, the most common coagulation disorder in overt hypothyroidism is acquired vonWillebrand’s disease.
• Recently, it has been shown that mean platelet volume in euthyroid patients with Hashimoto’s thyroiditis is significantly higher than the healthy controls (96).

Other side effects of Synthroid

Providing a complete list of medications to the doctor will help with getting the correct dose established for each individual patient. 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 (about 8 ounces) 30 to 60 minutes before breakfast for best adsorption into the body. Children can take the medicine if the tablet is crushed and put into about 1 to 2 teaspoons of water; do not store or delay giving this crushed pill suspension. Doctors often may have to slowly increase the dose; patients should not increase or decrease this medication themselves. Because some preparations of the drug may contain iodine or lactose, patients should tell their doctors about such allergies or reactions to these components. Clumps of hair falling out, thin eyebrows, and problems with body hair are all signs of low thyroid function.

• A proposed mechanism is direct effect of thyroid hormones as there are several studies in favor of a prothrombotic effect of thyroid hormones in the literature (19, 38, 44, 69).
• Measure and evaluate unbound (free) hormone and/or determine the free-T4 index (FT4I) in this circumstance.
• If SCH would have been proven to be a risk factor for VTE, this can change clinical practice and management of the patients as VTE would be re-classified as “Provoked” or “Non-provoked” based on the presence or absence of SCH.
• Reduced levels of FIX, FX, and FXI are reported (15, 24, 26, 38, 76).
• If so, advise them to stop biotin supplementation at least 2 days before assessing TSH and/or T4 levels see DOSAGE AND ADMINISTRATION and DRUG INTERACTIONS.

One sign that you’ve entered into hyperthyroid territory is a racing or irregular heart rate. If you’re having any heart issues at all, it’s important to call your doctor right away. They may or may not be related to your medications but you should get it checked out either way, she says. Like any medication, Synthroid can have side effects, but for most people, the drug just makes them feel awesome again, Goldfarb says.

Some side effects of levothyroxine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side synthroid fetus effects.

Patient Information for Synthroid

If you’ve got a rash, fever, exhaustion, or hives, call your doctor immediately, she says. They can switch you to a different type of generic or tell the pharmacy you need to be on the brand name. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Initial investigations revealed platelets of 238 (150–450), prothrombin time (PT) of 12.0 (12.0–17.0 s) and elevated activated partial thromboplastin time (APTT) of 41.0 (24.0–38.0 s). The elevation in APTT alluded to an intrinsic pathway abnormality which was investigated through further clotting factor analysis. This revealed reduced levels of chromogenic factor VIII 0.46 (0.6–1.3 U/dl), factor VIII clotting assay 0.4 (0.6–1.3 IU/ml), von Willebrand Factor antigen 0.31 (0.7–2.0 IU/ml) and von Willebrand Factor activity 0.39 (0.7–2.0 IU/ml). Initiation of thyroid hormone therapy prior to initiating glucocorticoid therapy may precipitate an acute adrenal crisis in patients with adrenal insufficiency. Treat patients with adrenal insufficiency with replacement glucocorticoids prior to initiating treatment with SYNTHROID see CONTRAINDICATIONS.

If you suffer from several or more of the above symptoms and are worried that you might have a thyroid problem, your next best step would be to visit your healthcare provider to get evaluated and discuss your options. You may also find it useful to learn more about thyroid testing beforehand to help you formulate good questions to ask your provider. If you’re not feeling quite right, it’s worth taking a closer look at the symptom list below.

That said, many women find their chronic headaches improve once the Synthroid kicks in. Although there are about 1 percent of patients that won’t respond to Synthroid at all and will need other treatment, the vast majority of people on it feel remarkably better within six weeks of starting it, she adds. Along with its needed effects, levothyroxine (the active ingredient contained in Synthroid) may cause some unwanted effects.