Drug-Nutrient Interactions Linus Pauling Institute Oregon State University

Unithroid is used for hashimoto’s disease, hypothyroidism, after thyroid removal, myxedema coma … Levoxyl treats synthroid maoi hypothyroidism (low thyroid hormone) and treats or prevents goiter. NP Thyroid is used for hashimoto’s disease, hypothyroidism, after thyroid removal, thyroid cancer … Tirosint is used for hashimoto’s disease, hypothyroidism, after thyroid removal, myxedema coma … Synthroid can be given to infants and children who cannot swallow whole tablets by crushing the tablet and mixing the freshly crushed tablet in a small amount (5 to 10 mL or 1 to 2 teaspoonfuls) of water and immediately giving the misture by spoon or dropper.

TYPES OF PATIENTS WITH HYPOTHYROIDISM

When signs and symptoms raise the index of suspicion, the clinician should obtain a serum TSH level (Figure 12,5–7,15–17). If the TSH level is within the normal reference range, other etiologies for the signs and symptoms that prompted testing should be sought (Table 41,2). If the FT4 level is normal, further thyroid or pituitary evaluation is unnecessary.

DRUG INTERACTIONS

The pituitary gland sends out TSH, which tells the thyroid to produce the thyroid hormones thyroxine (T4) and triiodothyronine (T3). The information presented by TraceGains is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. For many of the conditions discussed, treatment with prescription or over-the-counter medication is also available.

• The present study also showed that at the time of diagnosis of hypothyroidism, BMD was not significantly different from normal subjects.
• Because the thyroid can’t respond properly, the hypothalamus sends out more TRH and the pituitary keeps releasing more TSH.
• You may not be able to take Synthroid if you have certain medical conditions.
• In addition to primary and secondary hypothyroidism, other conditions may cause decreased levels of total T4, such as euthyroid sick syndrome and serum thyroxine-binding globulin (TBG) deficiency.

Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. In older patients, levothyroxine therapy is begun with low doses, usually 25 mcg once a day. Patients require a large initial dose of T4 (300 to 500 mcg IV) or T3 (25 to 50 mcg IV). The intravenous maintenance dose of T4 is 75 to 100 mcg once a day and of T3, 10 to 20 mcg twice a day until T4 can be given orally. Corticosteroids are also given because the possibility of central hypothyroidism usually cannot be initially ruled out. The patient should not be rewarmed rapidly, which may precipitate hypotension or arrhythmias.

Similar patterns of serum T3 changes occur when mixtures of T3 and T4 are taken orally, although peak T3 is lower because less T3 is given. Replacement regimens with synthetic T4 preparations reflect a different pattern in serum T3 response. Increases in serum T3 occur gradually, and normal levels are maintained when adequate doses of T4 are given. Desiccated animal thyroid preparations contain variable amounts of T3 and T4 and should not be prescribed unless the patient is already taking the preparation and has normal serum TSH.

• When signs and symptoms raise the index of suspicion, the clinician should obtain a serum TSH level (Figure 12,5–7,15–17).
• Dose may also need to be increased if medications that decrease T4 absorption or increase its metabolic clearance are administered concomitantly.
• The “optimal dose” was determined for each patient as that dosage of thyroxine being taken when the thyrotropin-releasing hormone (TRH) response was normal (ie, an increase in TSH of between 4.7 and 25 mIU/L).
• Do not store the crushed tablet/water mixture and do not administer it mixed with foods that decrease absorption of levothyroxine, such as soybean-based infant formula.
• A high level of TSH plus low thyroid hormone levels indicates hypothyroidism.

Some patients with hypothyroidism can be challenging to treat and require special consideration. Use this section to review the cases of Steve, Jennifer, and Diana to see how to effectively manage their hypothyroidism with SYNTHROID (levothyroxine sodium). Synthroid is a prescription medicine used to treat hypothyroidism (low thyroid hormone). Levothyroxine is given when your thyroid does not produce enough of this hormone on its own. A TSH test is used to check the level of thyroid-stimulating hormone in the blood. Your TSH level can indicate if your thyroid gland is working properly.

The administration of standard replacement amounts (25 to 37.5 mcg twice a day) results in rapidly increasing serum T3 to between 300 and 1000 ng/dL (4.62 to 15.4 nmol/L) within 4 hours due to its almost complete absorption; these levels return to normal by 24 hours. Additionally, patients receiving liothyronine are chemically hyperthyroid for at least several hours a day, potentially increasing cardiac risks. T3 does not cross the placenta and should not be administered to patients who are pregnant. Myxedema coma is a life-threatening complication of hypothyroidism, usually occurring in patients with a long history of hypothyroidism. Its characteristics include coma with extreme hypothermia (temperature 24° to 32.2° C), areflexia, seizures, and respiratory depression with carbon dioxide retention. Severe hypothermia may be missed unless low-reading thermometers are used.

Do not store the crushed tablet/water mixture and do not administer it mixed with foods that decrease absorption of levothyroxine, such as soybean-based infant formula. You may not be able to take Synthroid if you have certain medical conditions. Tell your doctor if you have an untreated or uncontrolled adrenal gland disorder, a thyroid disorder called thyrotoxicosis, or if you have any recent or current symptoms of a heart attack. With hypothyroidism, the thyroid is unable to produce enough thyroid hormone. The hypothalamus, located in the brain, produces thyrotropin-releasing hormone (TRH) that tells the pituitary gland to make thyroid-stimulating hormone (TSH).

Hypothyroidism:

Clinical hypothyroidism affects one in 300 people in the United States, with a higher prevalence among female and older patients. Symptoms range from minimal to life-threatening (myxedema coma); more common symptoms include cold intolerance, fatigue, weight gain, dry skin, constipation, and voice changes. The signs and symptoms that suggest thyroid dysfunction are nonspecific and nondiagnostic, especially early in disease presentation; therefore, a diagnosis is based on blood levels of thyroid-stimulating hormone and free thyroxine. Symptom relief and normalized thyroid-stimulating hormone levels are achieved with levothyroxine replacement therapy, started at 1.5 to 1.8 mcg per kg per day. Adding triiodothyronine is not recommended, even in patients with persistent symptoms and normal levels of thyroid-stimulating hormone. Patients older than 60 years or with known or suspected ischemic heart disease should start at a lower dosage of levothyroxine (12.5 to 50 mcg per day).

Certain foods and medications can interfere with the way your body absorbs or processes Synthroid. Be sure to let your doctor know if there are any changes to your diet or to the medications you take. You can see a list of the foods and medications that can affect the way Synthroid works here. Elisa shares her journey, from living with hypothyroidism and getting a diagnosis to starting—and continuing—treatment on Synthroid. Biochemical assessment incorporated measurement of serum TSH, T3, and T4. TSH lower limit of quantification was 0.2 mIU/L and upper limit of normal was 5.6 mIU/L, as indicated by the shaded area.