I am beginning by assuming that there is such a thing as a low thyroid
(hypothyroid) condition that, while technically outside the range of
parameters for the lab to detect, is still a condition which manifests
itself with symptoms typical of a clinically-recognized low thyroid
condition.  Wilson's syndrome is one fellow's explanation of the
problem.  Barnes did a lot of work with thyroid and concluded that as
many as 40% of Americans have a low thyroid condition.  Although I
think his estimate sounds quite high, he was probably on to something,
in my opinion.  I say all of this to ask the question: what is it that
might be causing the sub-clinical, low thyroid condition in so many
people these days?  What, specifically, either acts upon the thyroid
directly (heavy metals?) or acts on it indirectly (via a direct effect
on the pituitary gland, for example), that causes this widespread
problem?

Hi jat,

Good day and thanks for your question. I'm glad I got the opportunity
to answer this question since I have hypothyroidism.

The figure of 40% is not an inflated one. Many people are not aware of
this disorder as it is a relatively harmless ones. It gets harmful
only when the hormone levels reach extremes. In my case, according to
the endocrinologist, the cause of my hypothyroidism is a hereditary
one.

According to the Mayo clinic, the following are the other causes for
hypothyroidism :

* Autoimmune disease (Hashimoto's thyroiditis) : Autoimmune disorders
occur when your immune system produces antibodies that attack your own
tissues
* Treatment with radioactive iodine : People are treated for
hyperthyroidism with radioactive iodine, which reduces the function of
the thyroid gland. However, too much iodine could reduct it's function
too much, and hence cause hypothyroidism.
* Radiation therapy : Radiation used to treat cancers of the head and
neck can affect your thyroid gland and may lead to hypothyroidism.
* Thyroid surgery : Removing all or a large portion of your thyroid
can diminish or halt hormone production
* Medications : A number of medications can contribute to
hypothyroidism. One of the most common is lithium, which is used to
treat psychiatric disorders
* Congenital disease : Approximately 1 in 5,000 babies in the United
States is born with a defective thyroid gland or no thyroid gland at
all
* Pituitary disorder : About 1 percent of cases of hypothyroidism are
caused by the failure of the pituitary gland to produce enough TSH
* Pregnancy : Some women develop hypothyroidism during or after
pregnancy, often because they produce antibodies to their own thyroid
gland (Note : Women are very prone to hypothyroidism)
* Iodine deficiency
[ Source :: http://www.mayoclinic.com/findinformation/diseasesandconditions/invoke.cfm?id=DS00353&#Causes
]

The following links talk a lot about this condition :

Subclinical Thyroid Disease: A Clinician's Perspective
Annals of Internal Medicine, 15 July 1998. 129:135-138.
http://www.acponline.org/journals/annals/15jul98/thyroid.htm

Subclinical hypothyroidism
http://www.uptodate.com/patient_info/topicpages/topics/Thyroid/7267.asp

WebMD : Subclinical hypothyroidism
http://my.webmd.com/encyclopedia/article/4115.12809

Managing subclinical hypothyroidism
(Aust Prescr 1999;22;132-4)
http://www.australianprescriber.com/magazines/vol22no6/hypothyroidism.htm

Subclinical Hypothyroidism Sick Euthyroid Syndrome
http://www.fpnotebook.com/END187.htm


Links about hypothyroidism on the whole :

Hormones
http://www.dietitian.com/hormones.html
Hypothyroidism, dieting and weight loss. Ask the Dietitian SM.

Hypothyroid
http://www.hsc.missouri.edu/~daveg/thyroid/thy_dis.html#Hypothyroidp
Primary, secondary and juvenile hypothyroidism. Includes photo
illustrations. Division of Endocrinology and Metabolism University of
Missouri Health Sciences Center Columbia, Missouri.

The Clinical Hypothyroid Division: Children
http://www.magicfoundation.org/clinhypo.html
An explanation of this disorder and its causes, symptoms in childhood,
progression, diagnosis and treatment.

Hypothyroidism
http://www.endocrineweb.com/hypo1.html
Explanation of hypothyroidism. Illustrated. EndocrineWeb.com

Hypothyroidism
http://www.thyroid.org/resources/patients/brochures/hypothyroidism.html
Symptoms, diagnosis, treatment, secondary hypothyroidism. The American
Thyroid Association

I hope this answers your question. If you have any clarifications,
please feel free to ask

Good day and thank you for using this service

Warm regards,
aditya2k

Search Terms : hypothyroidism, subclinical hypothyroidism, causes

---

Request for Answer Clarification by jat-ga on 30 Nov 2002 22:14 PST

You gave me a good "bibliography" on hypothyroidism, but I don't think
you answered my specific question re: the reasons why so many people
are hypothyroid (subclinically, especially).  What is it that is
putting the thyroid out of whack in so many people?  Is it our western
diet?  Herbicides/pesticides?  Environment?  Heavy metals?  What? 
Let's try again, if you don't mind.  Thanks...

---

Clarification of Answer by aditya2k-ga on 30 Nov 2002 23:41 PST

Sorry about that jat, I guess I misinterpreted your question. Anyway,
here is some information I found pertaining to your question.

According to my endocrinologist, the number of reported cases have
gone up simply because the awareness has increased. Hypothyroidism was
unheard of in many households and people were not aware of the
consequences.

"A recent study in the Archives of Internal Medicine found that nearly
10% of reportedly healthy people whose thyroid function was tested
during statewide health fairs in Colorado had low thyroid levels. The
study's results suggest that people are not screened frequently enough
for hypothyroidism, and researchers recommend that doctors screen more
people for the disease and better educate them about its symptoms."
http://my.webmd.com/content/article/1728.56877

This awareness has led to rise in "reported" cases.

"Mild hypothyroidism (subclinical hypothyroidism) is most often caused
by Hashimoto's thyroiditis. Other causes include neck surgery or
radiation therapy and not taking enough thyroid replacement medication
for hypothyroidism"
"Pregnancy requires an increased production of thyroid hormones and
can cause hypothyroidism. About 3% of pregnant women in the United
States develop hypothyroidism"
http://my.webmd.com/encyclopedia/article/4115.12605

Medications : A number of medications can contribute to
hypothyroidism. One of the most common is lithium, which is used to
treat psychiatric disorders.

Another factor is iodized salt. Iodized salt provides the iodine
required for active functioning of a thyroid gland.
"More and more, people are eating wholesome, natural foods, avoiding
iodized salt"
http://www.sti.net/msgboard/health/_health/00000007.htm

"It has been shown that changes in endothelial function and
cholesterol concentration are apparent in subclinical hypothyroidism."
http://www.mercola.com/2000/oct/29/thyroid_tests.htm
From the above, it seems apparent that fatty foods contribute to
subclinical hypothyroidism. The chief culprit of fatty food entering
our body are the fast food chains (McDonalds, Burger King etc...)

Exposure to radiation, especially radioiodine has caused an increase
in certain places.
"A reported increase in incidence of hypothyroidism and of thyroid
nodules in Gomel oblast is also consistent with radioiodine exposure."
taken from
Effects on the Thyroid in Populations Exposed to Radiation as a Result
of the Chernobyl Accident
http://www.iaea.or.at/worldatom/thisweek/preview/chernobyl/paper2.html

"Subclinical hypothyroidism can develop in Graves' patients who have
been ablated even if they are on replacement therapy"
Graves' disease (GD) is an autoimmune disorder which primarily affects
the thyroid. No one knows what precisely causes Graves' Disease. It is
hereditary and occurs mostly in women. It is believed that a stressful
or life changing event, like the death of a spouse, can cause a
genetically pre-disposed person to develop Graves Disease, but not all
patients experience a stressful event. "
http://www.wfubmc.edu/library/gravesdisease.html

On the whole I feel it is the increase in awareness. However, even
today there are more people with thyroid disease than diagnosed.

I hope this answers your question. If you have further clarifications,
please feel free to ask

Regards,
aditya2k

A problem here is one of defintion. To say there are people who are
slightly hypothyroid when all lab tests are normal, it to invent a
disease for which there is no diagnosis. The definition of
sub-clinical hypothyridism is that there are no or very mild symptoms,
normal or slightly low thyroid hormone levels, and slightly elevated
TSH (thyroid stimulating hormone, made in the pituitary, and increased
to make the thyroid produce more thyroid hormone). So, if the lab
tests are entirely normal, to propose that there still may be
hypothyroidism is to get into a non-medical, non-scientific realm.
There are lots of para-practitioners (naturopaths, etc) who claim to
have other ways to test thyroid function. Such tests have not been
subjected to scientific rigorous proof; or when they have, they have
been found wanting. It may be true that there is more to be learned
about thyroid function and regulation: however, to define
non-scientific parameters as meaningful is entering into a world of
anecdotes, placebo-effect, etc. To talk about the condition, one must
either accept medical defintions, or not. If not, then there's a whole
world out there full of answers of unknowable veracity

I'm sure glad I didn't have to pay for that.  A typical case of
worrying about a precise definition, as though that, in itself, will
tell you "scientifically" that a person has low or sub-clinical low
thyroid.  The reason I react this way is that lab tests, for the most
part, reflect "normals" for a population sampled at a given period of
time.  "Normal ranges" are adjusted, ratcheted up or down, based upon
current population samplings, if I'm not mistaken.  It would be
interesting to note the "normal" range of parameters for blood work
done on, say, a previous generation.  What if 50% of the adult
population in this country has somewhat less thyroid function than two
or three generations ago?  We wouldn't be able to define that as "low"
or "sub-clinical" thyroid by today's measurements of "normal", would
we?

Ok, sorry, just trying to help, and to help you avoid pitfalls. You
can define normal anyway you choose, and have a nice day. There's
science, and there's opinion. More power to you.

One of the things I find extremely scary about internet health sites,
this one included, is the veritable panoply of un-peer reviewed
opinion bandied about as fact. What's even scarier is that someone is
paying $20 to get someone's very unscientific opinion. Were the
studies sited in respected journals? Were they prospective
case-matched randomized research?

Case definition is essential - without it, there's nothing to study.
Having a case definition does not obviate openmindedness and research.
As evidence based practice and research provides further information,
guidelines and practice will change. Until then, iterative opinion is
useless and anyone who follows such advice much less pays for it
should just take out a $20 bill and burn it.