I'm just curious because I...
- Don't have hashimotos.
- Haven't had children.
- Have not had thyroid surgery or been treated for over active thyroid.
- Have not been through the menopause.
And when I search for causes of hypothyroidism I don't tick any of the boxes.
Was I just genetically predispositioned to develop it?
I too have found no obvious cause for me. (Not that anyone other than me seems to have the slightest interest.)
Possibly the fact that I used to smoke? There seems at least some anecdotal evidence that some people become hypothyroid when they give up smoking, as did I, but that doesn't necessarily mean that smoke caused it.
Diets high in some substances called goitrogens can make people become hypothyroid - though that will often reverse when diet is changed.
Some compounds such as perchlorates (found in rocket fuel) are frequently quoted in the USA.
Have a look here for various thoughts about chemical causes:
Have you had any blood tests that show you are hypothyroid? Another cause, as I understand it, of functional hypothyroidism ie all the symptoms whilst having a performing thyroid, would be nutritional deficiencies. As your thyroid gland produces T4 which has to then be converted to the active form T3, any sub-optimal levels of the required minerals and vitamins could mean that your body can't convert this properly and hence your cells would not have enough T3 - hence functional hypo. There could also be other causes such as an issue with the pituitary gland that produces the TSH that tells your thyroid to produce hormones. I am sure there are others as well!
Gillian
Thank you.
Yes my original TSH was 31.9 and T4 of 9 (before treatment)
I've often wondered if it could be pituitary related but I think if it was I'd have low tsh, low t4 and low t3.
But the Dr's aren't interested in giving me an explanation especially now I'm 'in range'.
Oh well. Thank you for the information
Well one finnish endo has said that there are about 50 different genes affecting thyroid function so there could be at least 50 reasons on top of the obvious ones. Whatever switched the gene on or off is impossible to figure out.
Smoking for sure could be one although I have understood it just masks hypo and speeds up thyroid until you quit and the ugly face of hypo is revealed. But that could be the epigenetic change where smoking in the first place switches on or off certain gene which becomes a norm. When you quit smoking your body can't figure out why are you doing something so wrong big time as the epigenetic change fools your system to think it was and is normal and necessary to smoke.
Tobacco is endocrine disruptor in the end. If a woman smokes during pregnancy it affects for example the size and amount of fat cells of the fetus. Baby might be born underweight but as it now has been loaded up with bigger and more fat cells it will probably end up gaining weight in the future as the nature tries to correct the situation of low birth weight.
So tobacco as an endocrine disruptor is far more harmful than just a possible cause of lung cancer.
I believe mine was initially caused by an infection in the gum, and i keeled ocer after a bad chest infection. No familial relationship that I know of.
I believe that my problem was very low Vitamin D. I had no other symptoms like some others on here. I have corrected that now. I had my Thyroid removed last year and I am now on NDT before this I was not on any medication. There could be other reasons for you I hope that you find out. I am in fact only guessing that mine was lack of Vitamin D.
Thank you!
The smoking I haven't heard before and find very interesting. My mums side of the family have hypo in almost every woman but as a child I was exposed to a high level of passive smoking. Hypo only kicked in after I had my daughter. I do wonder what hi I have developed hyop if I was not subjected to passive smoking as a child? Food for thought.
I wondered if it was caused by the three head injuries I had - even though they weren't very bad - esp as mine is secondary/central - but I also have long-standing gut and fungus issues which might be related.
Leaky gut syndrome... allergic to wheat and dairy..? I didn't show obvious signs, though since i quit these in Jan cos of being diagnosed with hashimotos disease, cut these out and I am less puffy, weigh less and hoping to sort out the gut to reverse it. It all starts there. Hope you get it sorted and do your research on this 
Heard that the cause could also be because of being in damp environments causing candida when young..? There's a fair few other possibilities. Could also be a reaction to eating certain things or stress..
I'm not familiar with with this but I shall do my research. I am definitely sensitive to dairy and for the most part have cut it out. Grilled/baked cheese along with milk caused me to have severe diarrhea.
I am not sure about gluten, I don't seem to be sensitive to it. But I don't have hashimotos so I've never thought to cut it out. I have been tested for celiac but it was negative.
I am also beginning to think that it could be related to stress... It happened shortly after surgery and during my first year of university so there was a lot going on at the time. I've studied stress and it's effects and I'm beginning to believe this might be causing my prolonged muscle pain too.
Thank you for your reply
Yep, leaky gut - everything starts there... Look into L-Glutamine (not free form version)
Hypothyroidism
subclinical hypothyroidism what to do 
What else is wrong?
Pregnant...now what? Hypothyroidism
