Thyroid, underactive - Causes 

Causes of underactive thyroid 

An underactive thyroid (hypothyroidism) happens when your thyroid gland doesn't produce enough of the hormone thyroxine, also called T4.

Most cases of underactive thyroid are due to either the immune system attacking the thyroid gland or a damaged thyroid.

Immune system

Most cases of underactive thyroid happen when the immune system, which normally fights infection, attacks the thyroid gland. Doctors describe this as an autoimmune reaction. This damages the thyroid, which means it is not able to make enough of the hormone thyroxine, and leads to the symptoms of an underactive thyroid.

Hashimoto's disease is the most common type of autoimmune reaction that causes an underactive thyroid.

It is not clear what causes Hashimoto’s disease, but the condition runs in families. It is also common in people with another disorder related to the immune system, such as type 1 diabetes and vitiligo.

Treatment for overactive thyroid

An underactive thyroid can also be a side effect of treatment for an overactive thyroid, a condition where the thyroid gland produces too much hormone.

Treatment for an overactive thyroid, medically known as hyperthyroidism, can involve medication, radiotherapy or surgery, all of which can cause your thyroid to become underactive.

Other rare causes

A lack of iodine in your diet may cause an underactive thyroid. This is because your body needs iodine to make thyroxine. However, severe iodine deficiency is virtually unknown in the UK.

A viral infection or some drugs used to treat other conditions, such as depression and heart disorders, can cause the thyroid to stop working properly.

A baby may be born with an underactive thyroid if the gland does not develop properly in the womb. However, this is usually picked up during neonatal screening.

A problem with the pituitary gland could lead to an underactive thyroid. The pituitary gland is located at the base of the brain and regulates the thyroid. Therefore, damage to the pituitary may lead to an underactive thyroid.

Find out how to get a test for underactive thyroid.

  • show glossary terms
Deficiency
If you have a deficiency, it means you are lacking in a particular substance needed by the body.
Pituitary gland
The pituitary gland is a pea-sized gland in the centre of the head, which hangs below the brain and produces hormones.
Thyroid gland
The thyroid gland in the throat makes hormones to help control growth and metabolism (the process that turns the food we eat into energy).

Last reviewed: 13/10/2011

Next review due: 13/10/2013

Comments

4 Comments

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Comments are personal views. Any information they give has not been checked and may not be accurate.

DITHW said on 30 April 2012

This may be unusual however I feel that it is worth knowing how the male partner of the sufferer feels. My partner is another victim of apathy from her GP and has suffered from UT for a number of years in my opinion. What I wanted to say that it is very difficult living with someone who suffers with this and despite all that I try to do she does not see it. Now I acknowledge that we men in general and not good at dealing with emotional stuff but I have tried so hard .Her moods, temper, depression and apparent amnesia has once again raised its ugly head and I am being blamed for everything whilst she is unable to acknowledge her behaviour. Lately having visited this site I am comforted hugely after reading of the side effects of UT nearly all of which my partner suffers with. I feel helpless at the moment but thank fully she has found a consultant and Osteopath who agree she should be on Thyroxine but this is a few weeks away before we next meet the specialist.
I love her very much (or should I say the gentle, soft and unaffected side) but this has changed me and I feel depressed and de-energised and sit here typing this wanting to pack my bags but she needs me and hopefully we can get through it. So ladies if you can please at least consider what your partner is having to deal with which is not as bad as having the condition can be just as destructive. I have even considered if I am suffering with an UT- god help me.

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trixxyv5 said on 25 March 2012

I'm a 26 year old woman, and after having swine flu in 2009 my health has got quite bad. I had a routine blood test after I started getting sciatica in my back in october 2011 which showed I was slightly anemic and was borderline underactive thyroid. I had another blood test 2 months later and my doctor said my thyroid had got slightly worse but I was still only borderline so wouldn't put me on meds. She said to have another blood test in 3 years but surely if it got worse in 2 months it could get a lot lot worse in 3 years? Also, I've become a lot more tired lately, I need to sleep in the afternoon even though I sleep well at night. My hair is also falling out at the root more, my skin is ver dry and flaky and I feel I have no energy.I have also gone off sex and just seem irritable all the time.I did suffer depression about a year ago too. I did have a minor sinus operation over 2 weeks ago so I'm not sure if that's why I feel like I do. I've been back and forth to the docs for various things lately and don't want them thinking I am a hypochondriac but am getting slightly worried as I've heard what it can do if left untreated.

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Tulip7 said on 08 February 2012

This is the first time I have ever posted a comment on a website, but after reading your comment I thought I would register, so I could respond. I am a woman of 42 (43 in April) and have been on thyroxine since the age of 3. I should have been on thyroxine since birth, but the doctors would not believe my Mum when she said there was something that wasn't quite right. For a long time, on and off, my thyroxine levels have been up and down and I have been alternating between dosages between 150 and 175 daily. I understand how hard it can be to get the balance right. For example, 5 years ago, my dose was raised upto 200mg daily and then after a while I suffered with very bad heart palpitations for a week, as I obviously did not need so much thyroxine in my system at the time. From past experience, I understand what you mean about some individuals in the medical profession being unsympathetic/not understanding. I had been thinking about alternating different sizes of pill, cutting smaller ones up for instance. Last year I changed my Doctor's surgery and a Doctor at the new surgery suggested I try taking 175mg on weekdays and 150mg at the weekend. I had a blood test in January and had a 'Good T4 result'. Is it possible for you to change your Doctors's surgery or get a second opinion or fresh look at your situation? I sincerely hope you mange to get it sorted out. Best wishes.

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sheba12 said on 17 January 2012

Im a woman of 45years old & have had hypothyroidism since I was only 3 months old,I hate it,sometimes the medical profession are so unsympathetic,il tell you why,over the last seven years ,my condition has got worse,I had to give up working because I was sleeping at least 17 hours a day,was physically exhausted& drained and so depressed because of it,I was on a certain dose and I was getting a bit better ,had bit more energy&wasnt sleeping so much and was happier,I went for a blood test and to my horror my gp said my levels were too high ,so they reduced the dosage and back to my old ways,im so depressed coz of it and dont know how much more I can take!!!!Help sheba12

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