Beware the Zombie Thyroid!!

Periodically, I update metabolism.com with interesting problems from my medical practice. Last week I was reminded of a particular thyroid disease which is little known and deserves more attention. In my patient’s case, she had an inactive thyroid (hypothyroid) due to Hashimoto’s thyroiditis for several years which, on its own switched to become an over-active thyroid (hyperthyroid). I call this event a “Zombie Thyroid”. Don’t bother trying to look this term up since ‘Zombie Thyroid’ is my own terminology. A Zombie Thyroid is, of course, one which returns from the dead. Most times when the thyroid is destroyed by either natural forces or by human intervention, the destruction is complete and irreversible. Rarely however, a thyroid which ceased function for years resumes producing thyroid hormone and may even becoming “hyper” or over-functioning. Such was the case of my patient last week. Confusion may result because the newly risen thyroid begins adding thyroid hormone to the blood of someone already taking thyroid hormone replacement for hypothyroidism (under-functioning thyroid). Recognizing the Zombie Thyroid can take months or years due to the rarity of the condition and the subtlety of the changes that occur on blood testing.

The Zombie Thyroid occurs in the setting of either autoimmune thyroid disease such as Hashimoto’s thyroiditis or a structural thyroid disease, multinodular goiter. Hashimoto’s is the most common cause of naturally occurring hypothyroidism in women under the age of 60 years. Hashimoto’s occurs when the body creates an antibody to the thyroid, resulting in destruction or impairment of the thyroid tissue. It is thought that the thyroid can ‘return from the dead’ if the body begins to produce more of another type of antibody that results in stimulation of the thyroid tissue. The switch from under active to over-active can take months or years. During this time the combination of taking thyroid hormone pills for Hashimoto’s plus the new supply of the body’s own thyroid hormone production can result in disturbing and seemingly unexplainable high thyroid levels. Once it is clear that the thyroid is producing thyroid hormone again it is possible to make appropriate adjustments in medication to return the situation back to normal.

Another situation involving the Zombie Thyroid is seen in elderly people who have had an enlarged and lumpy (nodular) thyroid for years. Some of these “multinodular goiters” produce adequate amounts of thyroid hormone but others can be associated with thyroid hormone deficiency (hypothyroid). When the multinodular goiter causes hypothyroidism, the patient will be treated with thyroid hormone replacement just like the Hashimoto’s patient. Over time the nodules may slowly begin to wake up and begin producing thyroid hormone. If the patient is already taking thyroid hormone due to the previous diagnosis of hypothyroidism, the combination of the two sources of thyroid hormone can result in excess or “hyper” thyroidism. In the elderly the doctor may suspect the elevated thyroid hormone levels are the result of a medication error perhaps due to the patient’s forgetfulness. If no action is taken serious complications of hyperthyroidism can develop such as irregular heart beat, congestive heart failure, excessive fatigue, and mental or mood impairment. Some elderly patients become withdrawn and lose weight mimicking depression, a situation known as “apathetic hyperthyroidism”. Recognition of the Zombie Thyroid is essential to restoring the thyroid levels and the patient’s clinical status back to normal.

Don’t let yourself or loved one become a victim of this ‘back from the dead’ thyroid. Alertness is the key to recognizing and treating the Zombie Thyroid. Ask your own physician for advice if you suspect this condition.

This article is for educational purposes only and is not meant as medical advice. The disclaimer of metabolism.com applies to this and all my blogs.

Gary Pepper, M.D., Editor-in-Chief, metabolism.com