Thyroid Hormones 101: Hypothyroidism and Hyperthyroidism

Key takeaways: 

• The thyroid is a butterfly-shaped gland located at the front of our throats
• Thyroid-stimulating hormone (TSH) is made in the pituitary gland in our brains and tells our thyroid gland what to do
• The thyroid releases important hormones like thyroxine (T4) and triiodothyronine (T3), which have important roles in our metabolism, growth and (of course) our menstrual cycles
• These hormones can get out of balance and when we have too much (called hyperthyroidism) or too little of them (called hypothyroidism) it can cause problems in many areas of our health

Our thyroid hormones are a trio of hormones that all have really important roles in the body.

This love triangle influences a whole host of bodily functions, including our metabolism, our growth and development, our digestion, temperature, mood, heart health and of course, our periods, menstrual cycles and ovulation.

Seriously, these little hormones are always busy.

But just like many of our other hormones, our thyroid hormones are sensitive souls and can easily get thrown off balance.

So what are the symptoms of a thyroid imbalance? And how do we know when we should test our hormones to check in on our thyroid function?

Before we jump in, let’s recap on how our thyroid hormones work…

The thyroid hormone feedback loop

Just like lots of our other hormones (such as our cycling hormones), our thyroid hormones are all linked—involved in what’s known as a feedback loop.

Think of it like a relay race. One hormone offsets another and the next can’t get going until it’s had a signal from the previous one. This is why our thyroid hormones (and others involved in feedback loops) are super sensitive and can easily get off balance—because they all depend on each other to stimulate their effects.

Let’s take a look a the thyroid feedback loop:

1. Thyroid-Stimulating Hormone (TSH) is released from the pituitary gland in our brains (where lutenising hormone (LH), follicle stimulating hormone (FSH) and prolactin are also made)).
2. TSH then (you guessed it) stimulates our thyroid gland—a butterfly-shaped gland located at the front of our throats, to produce the hormones thyroxine (T4) and triiodothyronine (T3).
3. T4 is then converted into a slightly different form called triiodothyronine (T3).  Both T4 and T3 can be bound to tissues or circulate in the blood; the unbound versions are known as free T4 (FT4) and free T3 (FT3). .
4. FT4 and FT3 are carried off through the bloodstream to get about their good work.

Can thyroid hormones become imbalanced?

You betcha. Thyroid imbalances are really common and disrupt many aspects of your health—bringing on a whole range of unwanted symptoms. 

Thyroid hormone imbalances are caused by either an underactive thyroid (known as hypothyroidism) or an overactive thyroid (hyperthyroidism)

Let’s take a look at each in turn…

Underactive thyroid

Hypothyroidism is when your thyroid isn’t producing enough T4 (sometimes in combination with T3) and you have an abnormally high level of TSH in comparison. 

It can be caused by a range of factors including age, poorly balanced diets and pre-existing medical conditions such as polycystic ovary syndrome.

Additionally, taking certain medications such as oestrogen-containing hormonal contraception and high doses of steroids can interfere with thyroid function.

Because of the thyroid hormone feedback loop, when T3 and T4 are low our brains will overcompensate and produce more TSH to try and boost our T3 and T4 levels, resulting in the classic low T3 and T4 levels paired with high TSH reading seen in hypothyroidism.  

Most thyroid function tests will not measure T3 (or FT3) unless you are known to have problems with your thyroid.  This is because you are unlikely to have abnormal levels of FT3 without having abnormal levels of TSH and/or FT4.

Hypothyroid symptoms include:

• Fatigue
• Weight gain
• Heavy or irregular menstrual periods 
• Fertility issues due to irregular periods and irregular ovulation 
• Depression
• Constipation
• Trouble concentrating
• Poor memory
• Increased sensitivity to cold
• Poor appetite
• Slowed heart rate
• Decreased sweating
• Swelling of the face and neck
• Thyroid pain
• Joint and muscle pain
• Dry skin or dry, thinning hair
• Brittle hair and nails
• Low libido (sex drive)

Having an underactive thyroid can also increase the risk of developing long-term health problems such cardiovascular conditions, insulin resistance, nerve damage and a swollen enlarged thyroid (goitre). 

This is why it is so important to investigate symptoms and regularly test your thyroid hormone levels to check in with them.

Women are 5 to 10 times more likely to get hypothyroidism than men, of which it already affects 2% of people.

Treatments for hypothyroidism

Firstly, there are lifestyle changes that could improve your thyroid function. 

Eating iodine-rich foods like milk and dairy products, adding more white fish into your diet, adding some more eggs, beans, pulses or red meat for additional iron. Make sure you are supplementing with 10mcg vitamin D through October to March or consider year-round.

Stress is a big factor in many hormone imbalances and conditions. So, like always, try to find a stress management method that works for you. If you smoke, consider quitting. Cutting down on your alcohol intake can help too (a glass of vino here or there is still perfectly okay).

Of course, there are also prescription medications, like levothyroxine, that can replace T4. This is usually a pill but can also be taken as a liquid. Like all supplements and medications, this should only be taken once prescribed and checked by a health professional.

Overactive thyroid

Okay but what about hyperthyroidism? This is when you have an overactive thyroid, making too much T4 and T3. Hello feedback loop, this increase triggers your brain to make less TSH—giving the characteristic low TSH paired with high T3 and T4 readings. 

Much like an underactive thyroid, lifestyle factors like poor diet, smoking, alcohol, and stress can cause an overactive thyroid. As well as genetics, autoimmune disorders like diabetes or Grave’s disease and excess iodine consumption. Additionally, long-term problems with cardiovascular health and weight loss are associated with an overactive thyroid.

Symptoms of hyperthyroidism:

• Changes in mood, especially nervousness, irritability, restlessness, anxiety and depression
• Irregular menstrual cycles, decreased menstrual flow (hypomenorrhea) and missed periods (amenorrhea), which may cause fertility issues
• Frequent bowel movements or diarrhoea
• Heat intolerance and excessive sweating
• Increased appetite
• Unintentional weight loss, even if food intake is the same or increases
• Hair thinning or hair loss
• Difficulty sleeping and insomnia
• Persistent tiredness and weakness, difficulty exercising
• Thyroid pain
• Neck pressure, breathlessness
• Rapid heartbeat (tachycardia) — more than 100 beats a minute
• Irregular heartbeat (arrhythmia)
• Feeling of having a pounding heart (palpitations) 
• Increased blood pressure
• Muscle weakness
• Twitching or trembling
• Protruding eyes (exophthalmos)

Treatments for hyperthyroidism:

Too much iodine can make hyperthyroidism worse by leading the thyroid gland to produce too much thyroid hormone. Therefore, you should be mindful of rich sources of iodine such as kelp and seaweed which are food sources likely to lead to excessive iodine intake. Take extra care to check the ingredients list of any supplements that you are taking, such as multivitamins, or preconception or pregnancy vitamins, which are likely to contain iodine. 

Additionally, prescription medications like carbimazole can be prescribed to decrease the function of your thyroid. Beta-blockers, which are anxiety medications that help to maintain and decrease your heart rate, can provide symptom relief from a racing heart or heart palpitations.

If needed, surgical intervention to partially remove your thyroid gland can also be an option.

Testing your thyroid function

The good news is testing your thyroid function is super easy. All you need to do is test your thyroid hormone levels. 

With a Hertilty Hormone and Fertility Test, you can test your thyroid hormones alongside your other reproductive hormones to gain an in-depth understanding of your reproductive health.
Ready to get started? Take your online health assessment today.

References

• https://pubmed.ncbi.nlm.nih.gov/24789479/
• ​​https://www.nhs.uk/conditions/underactive-thyroid-hypothyroidism/symptoms/ 
• https://www.endocrine.org/patient-engagement/endocrine-library/hormones-and-endocrine-function/thyroid-and-parathyroid-hormones
• https://www.niddk.nih.gov/health-information/endocrine-diseases/hyperthyroidism https://www.nhs.uk/conditions/overactive-thyroid-hyperthyroidism/complications/ 
• https://www.womenshealth.gov/a-z-topics/thyroid-disease
• https://www.nice.org.uk/guidance/ng145/chapter/Context
• https://thyroiduk.org/if-you-are-hypothyroid/overview-of-hypothyroidism/
• https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
• https://www.nhs.uk/medicines/carbimazole/