Levothyroxine is the drug usually prescribed for hypothyroid. The response to this medication is not immediate. It will take 2 to 6 weeks for full therapeutic effect to be felt. There is regular monitoring of lab work because dosing adjustment is based upon TSH (and possibly T4 & T3 levels). The dose is adjusted between the 4th and 6th weeks until a normal TSH is achieved, and symptoms resolve without adverse reactions.
Taking the medication as prescribed means at the same time, every morning, on an empty stomach. This insures maximum absorption. If the medication is taken at night, it may cause insomnia. The dose should not be altered, or stopped abruptly, and the brand should not be switched. Different brands have different dosing bioequivilents.
The patient should be aware of symptoms of over medication (thyrotoxicosis), and under medication (hypothyroid). As well as the side effects & adverse reactions to Levothyroxine (e.g. arrhythmias) They should be aware of the symptoms of exacerbation of comorbidities like CVD (chest pain, shortness of breath, palpitations); diabetes (elevated blood sugars); and congestive heart failure (edema, activity intolerance, shortness of breath, fatigue). These can be precipitated by under or over medication and should be reported to one's provider.
The patient should be aware that they may have to take the medication for the rest of their lives depending on the cause of their hypothyroidism (primary, secondary, tertiary, iatrogenic, idiopathic etc.). Children with congenital hypothyroid may be able to stop taking their medication for a 2 to 8 week trial by 3 years old; and may be able to stop taking it altogether if their TSH remain normal. A post partum hypothyroid phase can occur 4-8 months after delivery and may last up to 9 –12 months. It usually, but not always occurs, after a phase of hyperthyroidism (American Thyroid Association, 2012).
The dosage of Levothyroxine is weight-based (1.6 mcg/kg/day); or 25 to 150 mcg/ day (0.025- 0.15 mg/ day). According to the Nursing Drug Handbook, the elderly are titrated up from a very low dose- 12.5 - 25 mcg/ day to prevent toxicity. Those with pre-existing cardiovascular disease are started at 25 - 50 mcg/day (Epocrates Online, 2014). Children are titrated to very high doses- up to 150 mcg/ day to meet the demands of growth & development. Adjustments are made in 12.5 to 25 mcg increments to achieve a normal TSH of 0.3 to 5.5 (Edmunds & Mayhew, 2013).
While the 1st line treatment for primary hypothyroid is synthetic thyroxine/T4 (Levothyroxine), 2nd line therapy could be Liothyronine (Cytomel). Liothyronine is a synthetic version of the natural thyroid hormone T3 (L-triiodothyronine). Dosage starts with 25 mcg PO daily, increased by 12.5-25 mcg/daily every 1-2 weeks; and for elders it is increased 5 mcg/daily every 1-2 weeks.
The thyroid makes far more T4, which is converted into the active thyroid hormone (T3) in peripheral tissues. Cytomel/T3 is less commonly prescribed for hypothyroid due to difficulty maintaining the correct dosage level. I have not search very hard yet for citable sources regarding under which circumstances one would prefer to use Cytomel/T3 over Levothyroxine/T4. would assume a trial of Cytomel is necessary when someone has not achieved euthyroid with Levothyroxine/T4. A person can have difficulty-converting T4 to T3 due to stress and adrenal insufficiency (a secondary cause of hypothyroid), in which case both Levothyroxine/T4 and Cytomel/T3 are contraindicated and the drug of choice is a steroid (Epocrates Online). There can also exists genetics reasons for impaired conversion of T4 to T3.
Shamon (2014) states, Cytomel is most commonly used in diagnostic testing for hypothyroidism, due to it's rapid onset and short half-life when given Intravenously. Further, there has been an ongoing controversy whether to use both T4 and T3 together for primary hypothyroidism. The addition of T3 to the levothyroxine/T4-only treatment is a topic of ongoing research and discussion.
ARMOUR THYROID & THYROLAR
Armour Thyroid is a natural, porcine-derived thyroid hormone replacement containing tetraiodothyronine (T4 levothyroxine) and iothyronine (T3), as well as T1, T2 and other components. This product was once the sole thyroid hormone replacement, and is still available in the U.S. It is prescribed by doctors who believe it is a better choice over Levothyroixine because it contains a full spectrum of thyroid hormones, that most closely mimic human thyroid hormones (Shamon, 2007).
For example, Dr. Andrew Weil (2008) prefers Thyrolar, another combo drug containing T4 & T3, when there is question whether the body is optimally converting T4 to T3 (e.g. during extreme physical or emotional stress). Saying that the combination seems to elicit a better effect than just the T4 in Levothyroixine. Theses naturally derived thyroid hormones have the same cautions and contraindications as the synthetic thyroid hormones: Levothyroxine (synthetic T4), Liotrix (synthetic T4 & T3 in a 4:1 ratio), and Liothyronin (synthetic T3).
INTEGRATIVE MEDICINE TIP: Thyroid Function Tests
American Thyroid Association.(2012). Postpartum thyroiditis. Retrieved from
Edmunds, M., & Mayhew, M. (2013). Pharmacology for the primary care provider (4th ed). St.
Louis, MO: Elsevier Mosby.
Epocrates Online. Monograph: Cytomel. Retrieved from
Epocrates Online. (2014). Hypothyroid: treatment options. Retrieved from
MedicineNet.(2003). What distinguishes the use of Cytomel vs. synthroid. Retrieved from
Nursing Drug Handbook. Levothyroxine: Indications & dosage. (Android version).
Shamon, M. (2014). The T4/T3 thyroid drug controversy: Thyroid hormone replacement with T4 and T3
drugs Vs. Levothyroxine alone. Retrieved from http://thyroid.about.com/od/t3treatment/tp/t4-t3