How Is the Thyroid Gland Like a Car?

Understanding the Complexities of Treating Thyroid Dysfunction

Written by Michelle Violi, PharmD – Women’s International Pharmacy

how is the thyroid gland like a carThe thyroid gland is a butterfly-shaped gland located in the front of the neck. It is responsible for producing hormones, which are essential for normal growth and development as well as regulating metabolism. Thyroid hormone function has been found to correlate with body weight and energy expenditure.

The thyroid gland produces two main hormones: levothyroxine (T4) and liothyronine (T3). T4 is an inactive thyroid hormone that must be converted to the active thyroid hormone, T3, before it can be used by the body.

Health care practitioners use testing and symptom evaluation to determine whether a patient’s thyroid gland isn’t working as it should. If the results indicate low thyroid function (hypothyroidism), there are a number of options they may prescribe:

Type of Thyroid PrescriptionExamples of Medications
Levothyroxine (T4) Only
  • Synthroid
  • Levoxyl
  • Compounded capsules
Liothyronine (T3) Only
  • Cytomel
  • Compounded capsules
A Combination of Liothyronine (T3) and Levothyroxine (T4)
  • Thyrolar (as of this writing in January 2019, on long-term back order)
  • Compounded capsules
Desiccated Porcine Thyroid

Taken from the thyroid gland of the pig, this contains T3 and T4, as well as thyroid cofactors such as T1, T2, calcitonin, and trace amounts of iodine

  • NatureThroid
  • Westhroid
  • WP Thyroid
  • Armour Thyroid
  • NP Thyroid
  • Compounded capsules

Levothyroxine (T4) only is the most commonly prescribed thyroid medication. However, this might not be the right choice in every situation. Because the thyroid gland plays a complex role in the body, some cases of thyroid dysfunction may require more than a “one medication fits all” approach.

Compare thyroid dysfunction to a car. When a car stops running, is it because it’s out of gas? Perhaps. In this case, fill up the tank and get back on the road. However, think of all the other possible reasons the car may have stopped running. The car may not be able to use the gas put in it or not use it well depending on whether the car needs diesel, premium, or regular. The car may be full of rust. The car may need oil or antifreeze, not gas. The list goes on and on.

In the case of thyroid function, there are also a wide variety of reasons why a thyroid gland may not be working. The thyroid gland may not be able to convert T4 to T3. The thyroid gland may be inflamed or be the target of an autoimmune response. The thyroid gland may need iodine, selenium, zinc, or other cofactors. As with a car, the list goes on and on.

If a patient with hypothyroidism is prescribed T4 only, the body must be able to convert T4 into T3 in order for the body to be able to use it. However, if there is an issue with this conversion process, the body may not be able to use a T4 only medication appropriately. Depending on what is wrong with the thyroid gland, additional support in the form of T3 or other thyroid cofactors such as are present in desiccated porcine thyroid may be needed.

As with so many things relating to health, optimizing thyroid function is complicated. If you are taking thyroid medication and still aren’t feeling well, don’t give up! Work with your health care practitioner and pharmacist to find a solution that fits your individual needs.

  • Muller R, Liu YY, Brent GA. Thyroid hormone regulation of metabolism. Physiol Rev. 2014;94(2):355-82.
  • Nature-Throid Availability Update. http://www.naturethroid.com/ Last accessed September 2019.
  • Treating Hypothyroidism. https://www.webmd.com/women/guide/low-thyroid-treatment#1. December 1, 2017. Last accessed September 2019.
  • Brownstein D. Overcoming Thyroid Disorders. 3rd West Bloomfield, MI: Medical Alternatives Press; 2008.