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.
This is the third most common thyroid problem in the US