Ten Simple Steps to Understanding Your Thyroid

A consistent challenge for new students in medical school is learning how to evaluate and treat thyroid disease. So if you have a thyroid issue, don’t feel overwhelmed. There are simple analogies we can use to make it understandable.

1) What is it?

It is a sponge-like gland in your neck that produces a fluctuating supply of hormone (T4 and T3) for your body to use.

2) What does it do?

The thyroid hormone gives us energy. Perhaps it is best to think of T3 as the gas tank in our cars. Without it, we feel sluggish and tired. Too much of it, and we bounce off the walls trying to burn off the extra energy.

3) How does it work?

Now, this is the more complex part. But, we can make it very simple by comparing the thyroid’s regulation to a society in which all you need to be happy is an apple a day.

Apples – T4 and T3
Money – Thyroid Stimulating Hormone (TSH)
The Government – The brain
Surveyors – blood stream

In this utopia, every citizen is guaranteed an apple a day. The apple factory (the thyroid) produces exactly the right number of apples (T4 and T3) for the number of citizens in the society. Surveyors (the blood stream) knock on everyone’s door to make sure that no one goes without an apple and reports back to the government (our brains).


When citizens are missing apples (T4 and T3), the government assumes that the factory workers need to be paid more to do their jobs. It throws money at them (an increase in TSH – thyroid stimulating hormone) to encourage them (Thyroid) to work harder. Thus, someone with hypothyroidism will have a high TSH (the brain’s attempt to stimulate the thyroid) and a low T4 or T3 (the circulating hormone produced by the thyroid gland).

When citizens have too many apples (excessive T4 and T3), the government assumes the factory workers are willing to work for free and stops sending them money (the TSH levels fall). Thus, someone with hyperthyroidism will have a low TSH (the brain seeing no reason to workers who will do their jobs for free), and high T4 and T3 levels.

Low TSH and High T4 and T3 = over active thyroid – hyperthyroidism
High TSH and low T4 and T3 – under active thyroid – hypothyroidism

4) What went wrong?

For hyperthyroid patients, a coffee machine (autoimmune antibodies) has been installed at the factory and the workers are over stimulated – called Grave’s disease. There can also be a section of the thyroid that is working harder than the rest. To expand on our factory analogy, Team “Show Off” has decided to out-produce everyone else. A thyroid scan is often ordered to see if the whole factory or just this small group of overachievers (called a “hot” nodule) is causing the problem. The endocrinologist will address these two problems in very different ways, so it is important to look inside the factory with the scan instead of just responding to the numbers.

For hypothyroid patients, the factory workers have decided to retire. The gland may stop working well because of age, genetics, and immune issues where the body develops antibodies (TPO) “apple haters” who slowly destroy the apple factory and harass the workers. Thus, the citizens of our utopian society don’t have enough apples to be happy.

5) How do we make it better?

For hyperthyroid patients, treatment involves either addressing the “hot” nodule directly or shutting down the entire factory with a medicine. The factory, in this case, is not salvageable and left to its own devices will produce more apples than anyone could eat. Shutting down the factory effectively gives the patient hypothyroidism whose treatment is discussed below.

For hypothyroid patients, the apple factory is in the process of shutting down. Some dedicated workers may still be producing apples, but the glands production may have dropped by 50% to 100%. The solution is to import apples. Luckily we have manufactured apples (levothyroxine pills) that are identical the T4 and T3 normally produced by the retiring gland. Low doses of this replacement are given in the form of a pill and then blood tests are done every 6 wks to check on the brain’s production of TSH. The numbers of imported apples are then changed (the dose of the medicine given) based on what the brain is paying. If it is paying more (a high TSH- Thyroid stimulating hormone) then the dose of levothyroxine will need to be increased. If the TSH is low (the government not wishing to pay more than it has too) then we need to lower the dose. If the TSH is in range, then we have found the right dose for our imagined society, and it is then kept at this dose for years. However, blood tests may be done every several months to ensure that more workers have not retired.

6) Are there exceptions?

When a person is stressed physically or from an illness, the brain can respond by trying to over stimulate its organs to make sure they are working at top efficiency. Thus, it may throw money (a high TSH) at a factory that is producing exactly the right number of apples (T4 and T3). This may falsely suggest that a person’s thyroid is failing/retiring when in fact it is working well. Called sick euthyroid, it is one of the reasons TSH levels are not always drawn in the hospital or, if abnormal, treated until they are rechecked. Once a person has returned home and recovered from their acute illness, the brain stops trying to over stimulate their thyroid and their numbers often return to normal.

7) Are there alternative treatments?

Armour thyroid is a supplement derived from desiccated pig thyroid and placing it into a pill. It is considered, by some, to be a more natural way of supplying the missing apples the body needs. Unfortunately, the number of apples (T4 and T3) stuffed into each pill can be variable and, on some days, every citizen in our apple-driven society may have five apples while on others they may not have enough. Some argue this more closely matches the natural variability of our endocrine system. The medical community, as a whole, feels it is much harder to regulate the correct dose a person needs if the pill dose is not a known fact and so tend to lean toward levothyroxine as a preferred therapy.

8) What are T4 and T3

Following our analogy, T4 is the packaged apple that still needs to be unwrapped before it can be effectively eaten. The T3 is the washed and cleaned apple, the T4 hormone broken down, and ready for immediate use.

9) What is Levothyroxine?

Levothyroxine is the most commonly prescribed thyroid replacement, and it is effectively T4 – packaged apples which the body then breaks down into T3 for consumption.

10) Is there a genetic link for thyroid disease?

Unfortunately, there is a genetic basis for developing thyroid issues and so if someone in the family has the condition others maybe at risk.

Having practiced medicine for over twenty years, I have developed certain analogies to help my patients understand their diagnoses. It is my belief that creating understandable models gives patients a sense of control over diseases that might otherwise feel overwhelming. Not all analogies work for every patient or every situation, and so this analogy should be disregarded if it confuses or a better alternative is discovered. None of what I have written should be considered medical advice, therapy, or in any way imply a doctor-patient relationship or treatment plan.

I hope this analogy helps. Be well.

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