Thyroid hormones blood test

The thyroid gland is part of the endocrine system and is responsible for controlling the metabolic rate (or pace) of all the processes in the body.  If there is a deficiency of circulating thyroid hormones, thyroxine (T4) and triiodothyronine (T3), every function of the body tends to slow down.  Conversely if there is over production of thyroid hormones, the metabolic rate speeds up.  Read more about how we can help hypothyroidism, Hashimoto’s disease or hyperthyroidism and Grave’s Disease here and read our published medical paper here

Thyroid Stimulating Hormone (TSH)

TSH is the hormone produced by the pituitary gland that helps control the thyroid gland.  TSH prompts the thyroid gland to make more thyroid hormones and usually increases when T3 and T4 levels drop.  When T4 and T3 levels become too high this switches off the production of TSH, by the pituitary, telling the thyroid to slow down production of thyroid hormones.

Free T4 and Free T3

This measures the amount of hormone produced by the thyroid.  T3 is the more active hormone and conversion from T4 to T3 is important to measure.  If T4 and T3 levels are normal despite an abnormal TSH, this may indicate an issue with the pituitary gland or reduced peripheral uptake of thyroid hormones.

Reverse T3

Reverse T3 (rT3) is produced as a secondary product and is not metabolically active.  There may be an increase in rT3 during conditions of stress. This is an optional add-on, only available through in-clinic phlebotomy.

Thyroid antibodies

Thyroid antibodies (anti-thyroglobulin and anti-thyroid peroxidase) are found in autoimmune thyroiditis such as Hashimoto’s or Grave’s disease, the most common forms of hypo- or hyperthyroidism.  The measurement of thyroid antibodies is accurate where, in contrast, the TSH value can fluctuate quite significantly and is less reliable.  It is also important to differentiate between autoimmune thyroid conditions and non-autoimmune as the nutritional approach is quite different. In addition, thyroid antibodies in the absence of altered TSH or T4 can indicate an increased risk of developing a thyroid condition in the future.

What is measured in this profile? 

• TSH
• Total and freeT4
• FreeT3
• FreeT3: FreeT4 ratio
• Reverse T3 (optional)
• Antibodies – anti-thyroglobulin (anti-Tg) and anti-thyroid peroxidase (anti-TPO)

 

Testing options:

You can choose to order an at-home test kit which includes all of the above measurements with the exception of reverse T3.  This is a fast, convenient and cost-effective way to measure (or monitor on an on-going basis) your thyroid function and health.