Feeling Blue? It Could Be Your Thyroid

By MARC SIEGEL, M.D.


    When a patient feels sluggish and depressed, the thyroid gland could be the culprit. Doctors are working toward developing a treatment program for psychiatric disorders stemming from hormone imbalances related to the thyroid.

    The thyroid is a bi-lobed organ buried beneath the strap muscles of the neck. It produces a hormone that can affect a person’s mood and metabolism. If too little hormone is secreted, a person may become tired or down, while too much thyroid hormone may result in an elevated mood or mania.

    It is crucial for physicians to screen their depressed patients for hypothyroidism. Often, a transition occurs over time from hyperthyroidism to hypothyroidism — an overproducing gland essentially burns out. This shift between the two extremes can happen over a matter of several weeks. Symptoms may include the patient feeling cold or being constipated, but frequently such a patient complains of fatigue and depression.

    It is well documented in the psychiatric literature over the past 10 years that depression improves when thyroid replacement is given. However, there is some disagreement over whether depressed patients with normal thyroid function should receive low-dose thyroid hormone as a trial. I am among the large group of internists and psychiatrists who would not consider such a trial unless the thyroid hormone production was at least slightly on the low side.

    My reluctance is because there is also a danger of over-treating low thyroid and provoking hyperthyroidism. The thyroid hormone levels in the blood must be carefully monitored. A change in dosing will reflect a change in blood levels but not for several weeks down the line.

    Both hypo- and hyperthyroidism are common in pregnant women, and either condition may lead to post-partum depression. It is important to test for thyroid disease throughout life, but especially during and immediately following pregnancy. Anxiety or fatigue in a pregnant woman could indicate that the thyroid is off kilter. But a subtle metabolic imbalance could also be clinically invisible, or masked by the symptoms of pregnancy itself, leading both patient and doctor to miss it.

    “Subclinical thyroid disease is discovered by testing, not clinical symptoms,” said Dr. Manfred Blum, professor of medicine and radiology and director of the nuclear endocrine laboratory at NYU. “A hunting expedition is launched by the doctor, sometimes finding hypo- or hyperthyroidism, both of which are found in the pregnancy and post-partum period.”

    Reports have stated that hypothyroidism during pregnancy can lead to impaired infant development. A study in the Journal of Obstetrics and Gynecology in 1999 confirmed that thyroid disease in pregnancy can lead to hypothyroid infants. Several European studies in 2000 and at Dartmouth in 2001 showed an association between maternal subclinical hypothyroidism and low IQ in the offspring.

    The good news is that thyroid replacement during pregnancy is completely safe and prevents problems from occurring in infants later on. Hyperthyroidism during pregnancy may lead to spontaneous abortion, but may also be safely treated with a medicine called propylthiouracil. Since propylthiouracil crosses the placenta, its dosage must be very carefully monitored.

    Hypothyroidism associated with post-partum blues is common (the gland is overactive during pregnancy and becomes fatigued after delivery) and often disappears naturally in a few months. Although the condition generally corrects itself, it may still be treated with thyroid replacement to combat depression.

    In fact, all patients who suffer from both depression and hypothyroidism seem to benefit from thyroid hormone replacement, as long as the blood levels are monitored carefully. If too much hormone is given, or if the condition improves without the doctor knowing it, then garden-variety depression can become a medicine-induced mania.

    Last month I was asked to see a manic patient for medical evaluation on the psychiatry ward at NYU Hospital. The patient was convinced that she had a problem in her neck stemming back to when she had been attacked 23 years earlier.

    When I read this patient’s chart, I discovered that her medical problem was actually an under-producing thyroid with an associated depression. I also discovered that she was on too much thyroid replacement. Hearing that her level was too high, her psychiatrist immediately decided that her recent mania was caused by this high dose and might well resolve with a dose adjustment. The patient’s preoccupation with her neck, while a psychiatric symptom, might also have been her intuition that something wasn’t right with her thyroid.

    To properly treat such a patient, a doctor needs to understand the complex interface between thyroid and brain, depression and medicine.
 

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Copyright © 1990-2007 Marc K. Siegel, M.D.