Sunday, January 6, 2008

Early effects of hypothyroidism

It is now Sunday evening and I am really starting to slow down. It was about 88 hours ago when I last took my thyroxine (Synthroid). It is a little early to feel weak and tired, but I think I have an explanation.

My daily dosage of Synthroid should have been about 150 mcg (micrograms). The dosage should be 2.2 mcg/kg, which is 152 mcg based on my body weight. My thyroid was functioning normally on December 13. On the 14th of the December it was removed. I started on 112 mcg of Synthroid on December 17th. The dosage should have been higher and I discussed this with Dr. Grist, however, it is immaterial since I would be going of the hormone in order to prepare for my radioactive iodine treatment.

Essentially, I have not had a "full dose" of thyroxine since December 13th.

I have also learned that the half-life of thyroxine is about 5-7 days. Since it has been almost 4 days since I had a dose, I am getting close to about a 50% concentration in my blood.

They way "half-life" works is every 5-7 days, the level of thyroxine in my body has dissipated by 50%. So:

  • After the first 5-7 days, I am at 1/2 the normal concentration in my blood.
  • After another 5-7 days, I am at 1/4 the normal level.
  • After the next 5-7 days, I am at 1/8th the normal level.
  • After the next 5-7 days, I am at 1/16th the normal level, and so on.

In any event, I feel the effects after 4 days because of the lower-than-normal dose I have had since December 13th, and because I now have stopped oral thyroxin completely.

I can't wait to see what I feel like in a couple of weeks! (Yee ha!)