Thyroid Hormone Replacement
The most common treatment for low thyroid hormone levels consists of thyroid hormone replacement therapy. The goal of thyroid hormone replacement is to relieve symptoms and to provide sufficient thyroid hormone to decrease elevated TSH levels to within the normal range.87
Conventional treatment almost always begins with synthetic T4 (levothyroxine) preparations like Synthroid® or Levoxyl®. Low doses are usually used at first because a rapid increase in thyroid hormone may result in cardiac damage.88
Sometimes hypothyroid symptoms persist despite T4 treatment. In a 2001 study, T4 therapy was no more effective than placebo in improving cognitive function and psychological well-being in patients with symptoms of hypothyroidism, despite improvement in free T3 levels.89 A December 2010 study compared the T3 and T4 levels of hypothyroid patients treated with T4 alone against the levels found in healthy people and reported that T4 supplementation alone did not increase T3 to the same level as found in healthy people.90 As you will read later, deficiencies in nutrients like selenium can disable the body from converting T4 to biologically active T3.
In an animal study, rats with the thyroid gland removed were treated with T4 alone. The researchers found that no single dose restored normal concentrations of TSH, T4, and T3 in the blood, tissues and organs.91 The following year the same authors reported that a combination of T4 and T3 was able to normalize hormone levels in both blood and tissues.92 Other studies have failed to demonstrate any advantage of the combination therapy, although the results do suggest the possibility of a subset of hypothyroid patients who would benefit from combination therapy.93,94
One combination option is a drug called Thyrolar, which combines synthetic T3 and T4 in a fixed 1:4 ratio. Caution should be used, however, in administering T3 to older individuals because excess T3 may cause adverse cardiac events in this population.95
Another T3 option is a drug called Cytomel®, which is a synthetic form of T3. This can be used in combination with T4.
Desiccated Thyroid. Armour thyroid, Nature-throid, and Westhroid are prescription medications that contain desiccated porcine thyroid gland. Natural thyroid extracts have been used since 1892 and were approved by the Food and Drug Administration in 1939. Armour thyroid and most other natural glandular preparations are made to standards approved by the United States Pharmacopoeia.
Armour thyroid is preferred by some clinicians because it may achieve results in patients that fail to respond to levothyroxine alone. Patients with hypothyroidism show greater improvements in mood and brain function if they receive treatment with Armour thyroid rather than Synthroid®.96 One argument favoring natural hormones is that other naturally occurring hormones and chemicals found in these preparations may buffer or enhance the effect of the active hormones.87,92
Ultimately, there may not be a single correct approach to low thyroid hormone levels. Instead, the best option may be to monitor thyroid levels through regular blood testing and systematically try various protocols to see what yields the best resolution of symptoms. Some people may prefer to begin with desiccated thyroid, while others may find it preferable to begin with T4 supplementation then move to a combination T3-T4 therapy if they experience no improvement from T4 alone.
Absorption of Thyroid Hormone Medications. Coffee,97 aluminum antacids,98 ferrous sulfate (iron),99 calcium carbonate,100 soy101 and possibly grapefruit juice102 can all decrease the absorption of thyroid hormone prescriptions. Most doctors simply advise patients to take thyroid hormone away from any food or medication.
While most people take thyroid hormone in the morning, a December 2010 paper suggests that it is more effective to take thyroid medication just before bed.103