Unexplained weight loss

My mother is 56 yrs old now. She begun to lose her weight continuously and slowly about 4 years ago, from 132lb to 110lb now. (Her height is 168cm).
During this process, she received almost all kinds of possible tests. The Diabetes and hyperthyroidism were firstly excluded. And she also received B ultrosonic, CT scan, gastroscopy and colonoscopy test, tumor marker test and so on. The results were normal. Her appetite is also the same as before and she eats as much as before.
So what could cause the weight loss? We are so puzzled.

[Red_Star]

Have they checked for any malabsorption issues such as Celiac disease?

[LivingInHope]

Did your mom used to lead a more active life style, where she used her muscles a lot more?  Muscle breaking down into fat can make a difference in weight- muscle weighing more than the fat it breaks down into as people age or don't use their muscles as much as they used to.  

What kind of testing did they do to rule out hyperthyroidism (did they test TSH only or were they more thorough)?  

While her appetite is the same, and she eats the same volume, has she changed the types of foods she's eating since it started?

Did she begin smoking around the time she started losing the weight?

[Shawe123]

Are there some other symptoms she's experiencing along with the weight loss?

[Cappuccinohot]

Thank you for your help. Yeah, she thought about this issue. But she never has any diarrhea problem. Is it possible that she is sufferring from malabsorption without diarrhea?

[Cappuccinohot]

Thanks a lot. She never changes her lifestyle. But she is almost a vegetarian and has suffered from sleep disorder for many years, which we don't know whether links to weight loss. She never smokes.

[Cappuccinohot]

Thanks.She has had sleep disorder for many years.  Following the weigh loss, she also got some hair loss. Additionally, her white blood cell count turned lower than the normal values.(around 3*10^9/L)

[LivingInHope]

What kind of sleep disorder does she suffer from?  

Has she taken a medication that has weight gain as a potential side effect which she discontinued prior to the beginning of the weight loss?

What test(s) did they run for thyroid?

Did they check her for autoimmune disorders, which can be associated with hair loss?

Did they refer her to a hematologist in regards to her white blood cell count?

[jemma116]

I know this is not a very nice thing to hear, but has your mother ever eaten undercooked meat like pork or barbequed pork sausages?

Is there a possibility that she may have eaten undercooked meat like pork, or drank contaminated water at some point and now has a tapeworm or other parasite?  I don't know if parasites would be detected by the tests that your mum has had.  

Possibly a stool sample would detect parasitic infestation.  But I am no expert on what tests need to be done.  What I do know is that with thread worms there is a very itchy bottom usually at night when the blighters come out to lay their eggs.  Sometimes you can see them wriggle out and sometimes they are excreted when we open our bowls.  

If your mum is eating lots and not exercising to burn it off, but is losing weight and all the tests have come back negative, it would be worth asking the doctor about it just to rule out the possibility.

With tapeworms, no matter how much you eat and eat,  the food is not digested becaue the tapeworm takes all the nourishment.  People then start to lose weight even though they are eating lots.

When my daughter was young she was constantly complaining of tummy ache and kept feeling ill.  People thought that it was because she didn't want to go to school (she loved going to school).  Then one day when she was extremely ill, with a very high fever and lots of pain and we were in the hospital, she went to the toilet to relieve her bowls.  I was shocked to see the amount of fat threadworms that had come out of her.  She used to suck her thumb so was picking up all sorts of germs and worm eggs that we cannot see by the eye.

Please do not be offended, but as your mum has had a few tests that have come back negative, there's no harm in checking this out.

Best wishes