and her serum TSH was still slightly elevated, as you can see, at 7. Her serum T4 again was perfectly within the normal range and only slightly higher than her previous T4 of 8. The levothyroxine was increased by 25 micrograms, or 25 percent in this case, to 125 micrograms a day. Eight weeks later, her fatigue had somewhat improved, but now she had new insomnia, and as you can see, her TSH was now below the normal range at .08 milliunits per liter.
This is a slide you just saw from Dr. Hamilton, and I would just like to reiterate that these small changes can have dramatic effects on serum TSH as we have seen in this patient.
This also brings the point of the log linear relationship between T4 and TSH. For every linear change in the T4, either free T4 or total T4 level, there is a logarithmic change in the serum TSH, again which was illustrated by this patient, a very dramatic drop in the TSH but a minimal rise in the T4 level.
So, what are the long-term effects of this low TSH, say, on this patient with a TSH of below .1? Well, now there are many studies showing that there are ill effects of a low TSH as well as a high TSH. Increased