Depression may be the first sign of an overactive or underactive thyroid. The nervousness, anxiety, and hyperactivity of hyperthyroidism often interfere with a person's ability to function in normal daily activities. Both anxiety and depression can be severe, but should improve once the hyperthyroidism is recognized and treated.
Depression is more commonly associated with hypothyroidism with its fatigue, mental dullness and lethargy leading to depression which is often profound and severe enough that a physician may mistakenly treat the patient first for depression without testing for underlying hypothyroidism. Since most hypothyroidism begins after age fifty, the symptoms are often attributed to aging, menopause and/or depression.
Approximately one in twenty women experience a change in thyroid function following pregnancy. Since this is a time when the responsibilities of the young mother are considerable, she may attribute the fatigue and emotional symptoms as a natural result of her increased duties and lack of sleep. Some physicians have suggested, however, that every young mother who experiences depression should have a TSH test to be sure her thyroid function is normal.
Bipolar is a relatively new term that psychiatrists are using to describe individuals whose emotions tend to swing from highs to lows, elation to the blues. A subgroup of this population experience rapid cycling, meaning that they have at least four major highs and lows per year. Studies of patients with rapid cycling bipolar disorder, (80% of whom are women) have shown that 25-50% have evidence of thyroid deficiency. Some feel well, and their only evidence of thyroid failure is an increased level of TSH in their blood. Others are clearly hypothyroid.
Physicians have prescribed lithium in the treatment of depression for years. It has a low incidence of side effects and a high success rate in treating depression, especially bipolar disorders including the rapid cycling described above.
Unfortunately, in individuals with an underlying tendency toward thyroid dysfunction, lithium may cause hypothyroidism. Since most physicians are aware of this relationship, it is now common for a physician to first check the serum TSH levels of a patient before prescribing lithium, repeating the thyroid test periodically while the patient is on the medication.
Not all individuals with depression have a thyroid problem. Nevertheless, because thyroid dysfunction can be so difficult to recognize yet so responsive to treatment, most physicians will order an initial serum TSH test to evaluate thyroid function.
You are at increased risk if you or a close relative has had a thyroid problem. Your risk is also increased if you have a related autoimmune condition such as diabetes requiring insulin treatment, pernicious anemia, or the white skin spots of vitiligo. You are also more likely to develop thyroid dysfunction if you or a close relative have had prematurely gray hair (one gray hair before thirty) or any degree of ambidexterity or left-handedness.
But why risk missing a thyroid problem if you are depressed? Discuss these concerns with your physicians and be sure that your TSH has been checked before you are treated for depression.
Medical studies done many years ago suggested that some allergic disorders seemed to occur with increased frequency among patients with thyroid problems.