Q: Lithium- Blood Tests & Interpreting TSH Results|
I have a question about when is it necessary to check lithium blood levels? I
am taking 600mg of Lithium (w/ no side effects) and my psychiatrist insists that
that's way below the toxic blood levels and hasn't tested my blood. At what
point should it be reccommended that my blood levels are tested? I think my
doctor may increase my lithium since the plan is to wean me off celexa and
possibly increase the lithium. He started at such low doses of lithium because
I am not clearly bipolar--but I definitely do not fall into the standard
depression or anxiety diagnoses.
I hope to hear from you soon. Please reply to my email, reguardless of whether
my question goes on your site.
And I love your website (psycheducation) I have learned sooooo much!
Dear LM --
Well, you're both right, basically. I often delay getting a blood test if I'm
not going above 600 mg of lithium.
And, it would be good to do a blood test now and then;
but the main things to look at would not be lithium level (although I'd get one
as long as you were getting your blood drawn) but thyroid (TSH) and a "baseline"
measure of your kidney function. Then, if you were doing well and the
medication was to be continued, I'd look at your TSH again at least once a year,
at least for the first year or two. I'm starting to check that TSH even more
often as I get more interested in how thyroid affects bipolar disorder, in order
to catch very early those folks who are going to head toward hypothyroidism on
lithium. I don't wait for them to get formally hypothyroid anymore, but instead
start thyroid replacement of one kind or another as soon as it's clear that
they're drifting north, i.e. that their TSH is going up.
In case you need it for those purposes, here's how to
Interpreting TSH results
TSH is the signal from your pituitary gland, up there
in the middle of your brain just under your
that tells your thyroid gland to "MAKE MORE" thyroid hormones. When your
gland makes too little hormone, TSH goes up. It's yelling:
"I said, make more thyroid hormone!" So a high TSH goes with hypothyroidism,
meaning too little thyroid hormone.
And, you guessed it, a low TSH happens when your
brain is seeing a lot of thyroid hormone. It no longer has to yell,
it's whispering now: "ok, ok, that's plenty already". And if your thyroid
levels were really high, the TSH would go down so low we
might not even be able to find it with a lab test.
Ok, well how low a TSH can you get and still be
okay? (Remember, as discussed above, and in more detail
hyperthyroid means increasing your risk of osteoporosis). That is, how far
can you push your thyroid dose up, before the TSH would go so low
you would be "hyperthyroid" and therefore taking risk with your bones?
Answer: nobody knows for sure. One research group has shown people who were
maintained "hyperthyroid" didn't get bone density decreases we usually
would have expected.Gyulai
For now, to be cautious, at least we shouldn't let
your TSH go below the lower limit of "normal" (0.4 uIU/mL -- forget the
units. Some labs now have a lower limit of 0.2, because their test is
different, so check the reference range on your test). Below that, most
experts would be worried about your bones. And there are some who would not
let your TSH get below the middle of the normal range due to this risk (around
1-2 is the "bottom" for many doctors I've worked with).
Published October, 2002