Hypothyroidism: treatment

Thyroid hormone replacement is the standard treatment for thyroid hormone deficiency. There are many preparations available with new formulations under development. All thyroid hormone preparations contain either T4 (thyroxine), T3 (triiodothyronine) or a combination of these two main thyroid hormones. Historically, the first replacement therapies available were preparations made of extracts from animal thyroids such as dried thyroid or thyroglobulin, and they worked quite well. However, problems with standardizing doses and maintaining uniform replacement lead to the use of the purified synthetic hormones alone.

T3 therapy requires multiple doses per day and can cause fluctuations in hormone levels, which many people feel. T4 therapy provides stable levels of both T4 and T3 in the blood and is the most common method of replacing thyroid hormone. Occasionally, a combination of T4 and T3 is used for treatment.

The best method of thyroid hormone replacement for you may depend on your own clinical situation. Occasionally, some experimentation with replacement methods is required to "reproduce" the natural levels of thyroid hormone that existed prior to the development of hypothyroidism. The best way to begin is with T4 replacement. It is the least complex way to replace lost thyroid hormones and with the correct dosage most patients feel completely normal on it. In addition to how you feel your doctor may assess your response by measuring your thyroid stimulating hormone (TSH).

Table 1: Common preparations and brand names of thyroid hormone replacement



T4 (thyroxine)

  • Synthroid®
  • Eltroxin®

T3 (triiodothyronine) pills

  • Cytomel®

T4, T3 combinations

  • T4 taken with Cytomel®

Desiccated thyroid

  • Thyroid Hormone®

Table 2: Methods of thyroid hormone replacement and advantages or disadvantages related to the different hormone preparations




T4 (Thyroxine) therapy

  • Once a day dosing
  • Uniform blood levels
  • Easily obtained

May not supply sufficient T3 in some cases

T3 (Triiodothyronine) therapy

 T3 levels are ample

  • May not supply sufficient T4
  • Blood levels fluctuate4

Combination T4 and T3 therapy

Attempts to mimic normal blood levels4

  • Additional cost
  • May not be required in most patients

Desiccated thyroid

"Natural" but from animal source

  • Uniform replacement can be problematic
  • Variable T3 levels over the day

What about thyroid hormone blocks?

Rare syndromes exist where thyroid hormone levels are normal but the hormone is "blocked" from having its full effect in the body. These are caused by abnormal receptors to the thyroid hormone. An endocrinologist can determine whether you have a block or "resistance" to thyroid hormone. Excessive replacement of thyroid hormone can have potential adverse consequences such as damaging your bones or heart. Consequently, taking high doses of thyroid hormone should be discussed with your physician before any course of treatment is started.

Will iodine tablets, kelp or seaweed supplements help?

Iodine supplementation is used to treat hypothyroidism caused by iodine deficiency. Because there is iodine supplementation in salt in North America and Europe, iodine deficiency is extremely rare in these regions. Occasionally, excessive iodine can cause a decrease in thyroid function, so it is important to discuss any home remedies or health food supplements for the thyroid with your doctor prior to taking them.

What about pregnancy and hypothyroidism?

Normal thyroid hormone levels are recommended prior to and during pregnancy. Thyroid hormones are natural hormones and do not hurt the developing baby. However, it is important to ensure that the dose of thyroid hormone you are on is correct throughout the pregnancy as often a dose adjustment is required as pregnancy progresses. The best test to follow during pregnancy is the TSH blood test. Your physician will be able to help you with the timing of the testing and any adjustments in hormone that may be required.

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