Q. Can lithium cause hypothyroidism in three months?

I'm quite sure I never had hypothyroidism before; have been slender and energetic all my life.  Further, my TSH, T3, and T4 levels were tested a year ago when I had my first manic episode and all were normal.  I began taking lithium three months ago, didn't have a baseline TSH test, but my new psychiatrist fixed that after two months on lithium and TSH was high, T4 was okay.  He ordered another test a few weeks later, and TSH was okay, but T3 and T4 were both low.  I have a referral to an endocrinologist in a month, but wondered about lithium causing this.  If I go off lithium will it go away, or is this an indication that I had an existing thyroid problem?



Dear Liz --
Yes, thyroid can change that fast; I've recently started looking at a TSH at about 3 months, not waiting for 6 months per the usual recommendations, because of a suspicion that things can go that fast, and wanting to get right on top of it with thyroid replacement. I wonder if you just check one more TSH (e.g about a month or so after your most recent one) if you couldn't save a trip to the endocrinologist (though that's not likely to hurt anything...), because my guess would be that by that time, you'll see the TSH clearly up compared to where you started.

Note that there is research showing people's bipolar depression responding better to treatment when their TSH is at the lower end of the normal range (0.5 to 2. 0, e.g.) compared to people whose TSH is near the upper end of the normal range, say 3 to 4.5. So unlike the endocrinologists, who don't start thyroid replacement until TSH is officially "abnormal", I start thyroid replacement, especially in someone on lithium, especially if their TSH is clearly going up, before they have an abnormally high TSH.

Dr. Phelps


Published December, 2003