Maurizio Fava, M.D.
Director, Depression Clinical and Research Program
Massachusetts General Hospital
There is an increase in frequency of bipolar disorder (also known
as manic-depressive disorder) among patients with autoimmune thyroid
problems. If you or someone in your family has manic or hypomanic
episodes manifested by days or weeks of feeling hyperactive, excitable,
and euphoric followed by days or weeks of depression with significant
fatigue and sleep or appetite disturbances that may interfere with
your normal activities, your physician may offer you medication
to control your mood swings and treat your bipolar disorder.
Lithium was one of the first medications that proved effective
for bipolar disorder as well as some other forms of depression.
The problem with Lithium is it may alter thyroid function. Lithium
may block the synthesis (manufacture) and the release of thyroid
hormone from your gland. Thus a patient who has autoimmune thyroid
disease may experience a drop in thyroid hormone blood levels after
starting Lithium. Lithium has also been associated with triggering
the onset of Graves’ disease.
Your physician will likely measure your thyroid hormone within
two to four weeks after starting Lithium. But if a psychiatrist
starts your Lithium he or she may not know that you have a thyroid
problem. Therefore you should be sure to tell the doctor that you
do have a thyroid disorder and need your thyroid level checked to
be sure there is no effect of the Lithium on thyroid hormone production.
Non bipolar clinical depression is a common condition in the general
population, but it is even more common among individuals with thyroid
disease. For this reason, if you experience periods of depressed
mood and/or lack of interest/motivation, accompanied by sleep or
appetite disturbances, fatigue, and decreased concentration, you
may be prescribed an antidepressant medication.
Zoloft is an anti-depressant that has been shown to be effective
in treating different kinds of depression. But if you are taking
thyroid hormone medication for hypothyroidism, you may have to increase
your dose if you start taking Zoloft. Fortunately these effects
are mild and it is likely that your thyroid hormone dosage will
not change very much if at all.
Although not everyone taking thyroid hormone experiences a need
for a different dose of thyroid hormone when they begin taking Zoloft,
it’s common enough that your doctor should order a T4 and
TSH test to evaluate your thyroid levels within a month or two of
your starting Zoloft treatment. If the Zoloft has lowered your thyroid
hormone level, you don’t have to stop Zoloft treatment. Rather
your physician needs to increase your thyroid hormone dosage and
recheck your T4 and TSH levels in a month or two to be sure the
adjustment is correct. Finally, it is possible that other related
anti-depressants of this type (SSRI’s or Selective Serotonin
Re-uptake Inhibitors) may have a similar effect on thyroid function.
These include Paxil, Prozac, Celexa, and Lexapro. Effexor has some
similarities to SSRI's as well and may have thyroid effects too.