HealthFirst

Underactive Thyroid

11th June 2025

Posted by Dr Michelle Wright

Welcome to another Health MattersDr Michelle Wright with you as usual.  Today, talking about something that affects millions of people but often goes undiagnosed: an underactive thyroid, or hypothyroidism. 

What is the thyroid, and what does it do?

The thyroid is a small, butterfly-shaped gland located at the base of the front of your neck. It might be small, but it plays a big role in regulating your metabolism, your energy levels, your mood, and even your body temperature. 

What happens when the thyroid is underactive?

When your thyroid is underactive, it doesn’t produce enough of the thyroid hormones – thyroxine and tri-iodothyronine (or T4 and T3 for short) – that your body needs to function optimally.  

What are the symptoms of an underactive thyroid?

Symptoms can be subtle and are often put down to other things – like stress, aging, or poor diet. Common things to look out for include: 

  • Fatigue – you feel drained even after a good night’s sleep. 
  • Weight gain – especially if you’re eating the same but still gaining weight. 
  • Cold intolerance – you’re the only one wearing a jumper on a warm day.  
  • Dry skin and brittle hair or nails. 
  • Low mood or feeling “slowed down” mentally. 
  • Constipation. 
  • In women, menstrual irregularities. 
  • And sometimes, fluid retention or hoarse voice. 

It’s important to note that these symptoms can come on gradually as thyroid hormone levels drop, and they may not all be experienced.  

What causes an underactive thyroid?

In Switzerland, the most common cause of an underactive thyroid is an autoimmune condition called autoimmune thyroiditis, where the immune system mistakenly produces antibodies that attack the thyroid gland. This gradually damages the gland, reducing its ability to produce thyroxine. 

How is hypothyroidism diagnosed?

The good news is, it’s simple to test for an underactive thyroid. A blood test for something called TSH – thyroid-stimulating hormone – measures how hard your body is pushing your thyroid to produce hormones. If your TSH is high, that means your thyroid is underperforming. 

Your doctor may also check the levels of your thyroid hormones. And a blood test for thyroid antibodies may be done if the cause is thought to be autoimmune. 

What is the treatment?

Hypothyroidism is usually treated with a daily medication called levothyroxine, a synthetic version of the hormone your body isn’t producing enough of – a safe, affordable, and very effective treatment. 

Once you’re on the right dose, symptoms usually improve over weeks to months – but it does require regular monitoring, especially at the beginning. 

So, do talk to your doctor if you notice any of those symptoms I mentioned.  

You know your body best – if something feels off, don’t ignore it. A simple blood test could make a world of difference. 

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