TSH levels dropping with no thyroid

[davidsqueen]

I had a complete thyroidectamy 6 weeks ago.  My first TSH level was normal (for having no thyroid) at 31.  When I reached 40 I was to have the radioiodine scan.  Since the first TSH test my levels have been consistantly dropping every week.  I went from 31 to 28 to 25 and now 18.  How can this be when I have no thyroid?  I confimed with my endocronologist last night that 95% of my thyroid was removed and he says that 5% is not enough to continue working and returning my levels to normal.  He says "I have never seen anything like this, but it's not necessarily a bad thing."  How can it be good?  Isn't this like being able to see without any eyes or something?  It should not be physically possible.  My endocronologist also says that if the level does not start dropping on its own he will inject me with human TSH to force the levels to rise so he can do the radioactive scan.

So my question is How can this be?  and Have you ever heard of this? and Is human TSH safe?

Thanks

Sarah

[shmaners]

Sarah,

I had a similar situation, with a TT on 7/24.  My doctor (surgeon) wouldn't proceed with the ablation until my TSH reached 50, so after 4 weeks, it was finally 42.25 and we thought we were getting close.  Until it dropped from there to 41, and then down to 37.  The docs seemed quite surprised, but attributed it possibly to my age (28) and said I'd get a lower dose of RAI to kill off the remaining tissue, then come back for the higher dose at a later date (which, incidentally, that radiologist thought would be in a couple of weeks).  Well, I was supposed to go in for my 2nd RAI treatment this week, until my surgeon called me and cancelled, saying it's not a good idea to administer two radioactive treatments so close together.  She said she'd start me on the hormone now, and I'd have to go off again (and wait for my levels to hit 50 again) in 4-6 months before proceeding.  My doctor never mentioned anything about a TSH injection.

How frustrating it has been.  I have recently seeked out an endocrinologist and will be getting an additional opinion next week.  The doctors (radiologist included) seemed to think my story was quite something, they'd not seen this before, and I come from a largely medical city, where it seems nothing is too strange.

I haven't had a FT-3 or FT-4 yet...(I'm not sure what that is, obviously I have more research to do) but I'll be looking into that.  Good luck.

[Mark Lupo, M.D.]

While TSH antibodies may be the case, the more likely cause is a larger remnant than usual.  If this is thyroid cancer and the TSH is on the drop then there is more thyroid left in than expected.  

Thyrogen (TSH injections) could over-come this in order to treat with RAI -- this is safe and used routinely for thyroid cancer follow-up studies.  

Would consider a careful neck ultrasound to see how much thyroid remains.  Because the TSH went to 31 at one point, there is not likely much.

[lknnc]

Stimulating antibodies could be the cause. Maybe they took out less than 95%?  Maybe you have thyroid tissue in other parts of your body?  It does happen.

Don't know about the injection of TSH to force levels to rise.

Have they run any other tests on you like the FT-3 and FT-4?