Can one be hypothyroid with almost no symptoms

Hello everyone,

I am a 29 y/o female who has always been interested in health and natural prevention. As such I have always read a lot on various health topics, supplements, natural cures, etc. I find these things fascinating.

Naturally, whenever I had an ailment, I researched it extensively.

I have had an underactive thyroid since adolescence. I did not do any blood tests until I was in my 20s, but ever since I was 13-14 I have had various symptoms that I later learned were associated with being hypothyroid: dry skin (white flakes if I scratched it), constipation, sensitivity to cold, water retention and waking up with very puffy eyes after a salty dinner the night before, and most importantly a veeeeeery slow metabolism and digestion--I would easily gain weight if I ate "normally" (three solid meals a day), so I only ate two small meals a day to stay at a normal weight. Also, "normal size" meals result in bloating very easily--my stomach when empty or when I have been eating only small meals looks many pounds lighter than when I have just had a big meal (which for most people would be simply a "normal size" meal).

When I learned about hypothyroidism, I measured my temperature and took blood tests and sure enough, my temperature was consistently low and my TSH was around 3, with Free T3 on the low end of the healthy range.

I've been able to eliminate some symptoms over the last few years: the dry skin and constipation went away thanks to various supplements and healthy foods, but some symptoms remain--most notably, the slow metabolism and slow digestion: I can go an entire day without eating and generally need to eat around 1,000 calories (or less) to avoid gaining weight. (I've tried the "eat more to speed up your metabolism" approach and the only result was that I gained weight and felt sluggish and "heavy" from all the food.) Whereas when I eat little (1-2 meals a day), I feel much better, "light", and very energetic.

I had another blood test in 2011 (my first one had been in 2006) and one last year. The results were:

2011: TSH 1.03 (down from the 3 level I got after my first test and probably a result of the diet and supplements I was following), Free T3 3.87 pmol ("healthy" range 2.6-5.7).

2013: TSH was up to 3.65 (no significant changes in diet etc.) Free T3 2.5 pg/mL (healthy range 1.7-3.7)

So it looks like my thyroid activity is fluctuating somewhat, even though I have not really noticed any change in symptoms over the last few years (as I mentioned, I no longer have constipation or dry skin).

Which brings me to my question--is it possible to be slightly hypothyroid but be healthy, i.e. to have a naturally slower thyroid? I ask this because I have never experienced some of the main symptoms of hypothyroidism: mental fatigue ("mental fog"), physical fatigue or sluggishness, depression, high cholesterol levels, muscle weakness/aches. On the contrary, I have always been very energetic--I go salsa dancing for 3-4 hours at a time multiple times a week, recently I spent the whole day skiing with almost no breaks, and mentally I have also always been very sharp, great memory, quick learner, always a straight-A student, always praised for my "intelligence" and sharpness, etc. I can also easily function quite well on little sleep (5-6 hours a night), though I do like to sleep in on weekends.

I should mention that I probably inherited my metabolic profile from my paternal grandmother, we seem to have very similar physiologies. Both of us are the type that would have survived very well in times of famine.

As a side note, I am 5'4'' and my weight (since high school) is around 125 lbs, +/- 5 lbs (I try to not let it go above 130). However if I ate "normally" I could easily go up to 150 lbs, as I did during my first two years of college when I had to be on their meal plan and it was hard to resist eating three "free" buffet meals a day, complete with chocolate chip muffins for breakfast, etc. Once I went off the meal plan, I quickly went down to around 130, and over the past few years I've tried to keep it around 125 (the salsa dancing helps a lot). In other words, I am not "overweight", but could easily become so if I ate what most people consider a "normal" (not excessive) amount of food.

In other words, other than the very slow metabolism and digestion (with the resulting bloating when I eat large meals), I do not really have any other major symptoms to complain of, even with a TSH of 3.65 (as of last year--I will probably test it again later this year; I did test my cholesterol and triglycerides recently and both came out great, as usual).

I experimented with taking thyroid supplements (including natural thyroid hormone--ThyroGold) and I did feel warmer for a while and my metabolism seemed to speed up a little, but those effects were temporary, almost as if my body wanted to go back to its "normal levels", so I stopped taking them as I felt no other benefits. I know a lot of people who take them say that the "mental fog" has cleared and they have more energy, but in my case there was never any mental fog, or sluggishness, or low energy.

Thoughts?