General Medicine

» Elaine Moore - subclinical hypothyroidism

Hi Super Squirrel,
I'm sorry I missed this post when I returned from vacation, and I apologize for the delay in getting back to you.
A large nutrition study (NHANES Study) showed that most normal adults have TSH levels between 0.3 and 1.0 mu/L. Based on these results and other studies, the TSH level has been lowered several times within the last few years. Now, a TSH higher than 2.5 suggests hypothyroidism. And for the last decade it's been reported that individuals with thyroid antibodies are likely to be hypothyroid with TSH levels higher than 2.0.

Your symptoms sound very much like those of hypothyroidism although amenorrhea is more likely to be seen in hyperthyroidism. This can vary though and considering your occupation you may have a lower body fat that's contributing to the absent or scant menstrual periods.

Doctors who specialize in Wilson's syndrome (not recognized as a condition by some endocrinologists) understand that basal body temperature is more relevant than blood tests. And doctors in the know realize that the TSH range has changed even though most labs are still using the ranges that come with the testing kits and these are rarely updated. The idea here is that endos will keep up with the latest recommendations.

Also important is the fact that TSH results can be misleading. They're falsely decreased in endogenous depression, night shift workers, and people with TSH receptor antibodies. These antibodies can cause hypothyroidism yet the antibodies keep TSH from rising. In a condition known as central hypothyroidism TSH is also low as the normal pituitary/hypothalamic/thyroid feedback mechanism is disturbed. The lack of TSH production causes hypothyroidism. Normally, TSH orders thyroid cells to produce a constant rate of thyroid hormone.

I hope that before your doctor proclaimed your thyroid fine he or she ran tests to measure your actual thyroid hormone levels, optimally your FT4 and FT3 levels and also tests for thyroid antibodies.

You might want to consider seeing another doctor. Through the thyroid board at about.com where I answer questions in The Ask Elaine Moore link, there's a referral page for recommended doctors. After our last move I found my doctor via this referral page. Hope this helps, Elaine