I am a 25-year-old male competitive distance runner.  Recently, I have
noticed that under hot and humid conditions, I hardly break a sweat. 
A few days ago, I did a 16-mile run in 80+ degree heat with full
humidity.  At the end, I was extremely hot and red-faced, but
bone-dry.

My performances in both races and workouts suffer during hot and humid
conditions -- more so than they should given my fitness level -- and I
believe the underlying cause is my inability to dissipate heat.

I've done countless searches on 'hypohidrosis' and 'anhidrosis' but
can't seem to find the definitive cause of my problem and a course of
treatment.  I have stumped many doctors.  Help would be very much
appreciated... I'm dying to run fast again!

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Clarification of Question by demecj02-ga on 22 Jun 2005 18:22 PDT

I also wanted to add that this is a relatively new problem.  In
previous summers, I would finish runs fairly sweaty -- never drenched
-- but looking like I just had a good workout.  Now, I hardly sweat at
all.  And my fitness level is about the same... I've been running
3000-4000 miles per year for the last several years.

I've also explored the thyroid connection.  In April 2004, my TSH was
4.0, and in June 2005, it was 2.6.  All other blood work was in the
normal range.

If you can get to the bottom of this, in addition to the $20, I will
name my second kid after you. :)

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Request for Question Clarification by umiat-ga on 22 Jun 2005 21:27 PDT

Hello, demecjo2-ga!
 You certainly have an intriguing problem. However, the fact that you
have "stumped many doctors" would certainly make GA researchers more
than hesitant to try to answer your question. We are not doctors, and
it is likely that we could offer you no more information than what you
have found in your own searches combined with the conditions your
doctors have ruled out.
 Have the doctors offered any potential diagnoses, or performed any
tests other than thyroid hormone levels? Also, in your own searches,
what conditions have you ruled out? Do you have any other unusual
symptoms in your daily life when you are not running? This information
would certainly spare a researcher many hours of searching in the
wrong direction.
umiat

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Request for Question Clarification by umiat-ga on 22 Jun 2005 21:32 PDT

For example, if you have ruled out the conditions that normally cause
anhidrosis, like those on the following site, is there some other
direction you imagine we might follow? 
http://chronicfatigue.about.com/gi/dynamic/offsite.htm?zi=1/XJ&sdn=chronicfatigue&zu=http://www.nlm.nih.gov/medlineplus/ency/article/003219.htm

bkdaniels,

I really appreciate your help.  Thanks for checking in.  Since I
originally posted my question, I had a more complete thyroid test
done, and here are the results:

Free T3: 2.63 pg/mL [2.3-4.2]
Free T4: 0.57 ng/dL [0.7-2.0]
TSH: 3.02 [0.3-3.0]
Antibodies Peroxidase: 250 [should be under 35]
Antithyroid Globulin: <20 [should be under 40]

The doctor prescribed 100 mcg Levoxyl, and I've been taking the
generic for the past week.  I am now totally drenched with sweat after
easy 60 minute runs, whereas just a week ago I could run for a couple
hours and hardly perspire.  I think the problem is solved... hopefully
in a couple weeks my running times will improve as well.

If you happen to see this post again, I have a quick question, if you
don't mind.  One of my primary goals currently is to qualify for the
Olympic Trials in the marathon.  The standard is sub-2:22, or 5:25 per
mile.  While I have never run a marathon before, I probably could have
run 2:25-2:27 before this problem cropped up.  Since an underactive
thyroid has most likely been the cause of my running troubles over the
past year, what are the ideal values I should shoot for to maximize my
perofrmance?  I'm assuming the range would be tighter for a marathon
runner, given the thyroid's role in getting oxygen into cells.  That's
my understanding, but I'm not a doc!

Thanks very much for your help.