What is postsurgical hypothyroidism?

Hypothyroidism is a disorder that develops when there is not enough thyroid hormone in the body to meet the demands of the organs and tissues that are regulated by its activity. Different processes may contribute to a deficiency of thyroid hormone. Patients with Graves’ disease who have undergone thyroid surgery may develop a condition known as postsurgical hypothyroidism.

In the setting of Graves’ disease, the overall goal of thyroid surgery is to remove an adequate amount of the thyroid tissue that produces and secretes excess amounts of thyroid hormone. If an inadequate amount of overactive tissue is removed during thyroid surgery, a patient may have persistent hyperthyroidism. More aggressive surgical approaches that are targeted to remove adequate amounts of overactive tissue may also involve the removal of significant amounts of normal thyroid tissue. Over time, this may lead to an overall deficiency of thyroid hormone. In some respects, this condition may be considered to be a desirable outcome of therapy. Patients who develop postsurgical hypothyroidism shift from an overactive state that may be difficult to monitor and control to an underactive state that is usually easy to manage with effective treatment.

What are the symptoms of postsurgical hypothyroidism?

Patients who develop postsurgical hypothyroidism may report a range of different symptoms that reflect an overall deficiency of thyroid hormone. These symptoms may become evident over the course of a few weeks, or they may gradually emerge over several months or years. Some patients may begin to notice that they are unable to tolerate cooler temperatures that feel perfectly comfortable to others around them. This symptom is called cold intolerance. Some patients may experience a substantial amount of weight gain due to changes in rates of energy consumption and metabolism. Some patients may feel tired and lethargic most of the time, sleeping for long periods of time without feeling energized or refreshed. Changes in behavior may be noted by friends, coworkers, or family members. Some patients may notice a decreased frequency of bowel movements.

What are the physical signs associated with postsurgical hypothyroidism?

Physical signs that may become apparent in patients who develop postsurgical hypothyroidism reflect the effects of an overall deficiency of thyroid hormone. Patients may be noted to have slow heart rates that reflect decreased stimulation of the cardiovascular system. If measurement of the pulse reveals that a patient's heart is beating at a rate that is less than 60 beats per minute, this condition is called bradycardia. Examination of patients who develop postablative hypothyroidism may reveal cool dry skin that is rough in texture. Characteristic skin changes may be related to decreased blood flow due to constriction of blood vessels in the tissue supporting the skin. Neurologic testing of patients who develop thyrotoxicosis may reveal characteristic findings related to decreased stimulation of the nervous system. Testing of the reflexes may reveal evidence of delayed relaxation of muscles when tendons in the arms, knees, and ankles are tapped with a reflex hammer.

How is postsurgical hypothyroidism diagnosed?

A diagnosis of postsurgical hypothyroidism can be made when blood tests reveal changes in thyroid hormone and TSH levels that are consistent with an overall deficiency of thyroid hormone. Doctors following patients with Graves’ disease who have undergone thyroid surgery are usually aware of the high likelihood that these patients may eventually develop postsurgical hypothyroidism. As such, these doctors usually make arrangements to check thyroid function tests on a regular basis to keep track of changes in thyroid hormone and TSH levels.

The actual thyroid function tests that are checked to monitor a patient's response to thyroid surgery may vary over time. While TSH levels usually provide the most sensitive indication of whether there is an adequate amount of thyroid hormone present in the body, they may not provide accurate information during the first few months after thyroid surgery. Long-term exposure to excess amounts of thyroid hormone may suppress the function of the cells that produce TSH in the pituitary gland to a point where it may take a period of several weeks for them to recover. During this period, TSH levels may remain suppressed, even after the amount of thyroid hormone in the body has returned to a normal level. For this reason, the amount of thyroid hormone in the body is usually measured directly during the first few months after thyroid surgery. This usually involves checking thyroid function tests that measure T4 levels, free T4 levels, or T3 levels. Serial thyroid function tests checked during this period may show a progressive decline in the amount of thyroid hormone present in the body as T4, free T4, and T3 fall below normal levels. If this decline is sustained, the pattern that emerges may be consistent with a diagnosis of postsurgical hypothyroidism.

Over time, as the cells that produce TSH in the pituitary gland gradually recover, they begin to secrete normal amounts of TSH that accurately reflect exposure to thyroid hormone. Once this recovery has occurred, TSH levels can be checked to monitor a patient's response to treatment. Serial thyroid function tests checked during this period may show a progressive increase in TSH levels that reflect a progressive decline in the amount of thyroid hormone present in the body. If this increase is sustained, the pattern that emerges may be consistent with a diagnosis of postsurgical hypothyroidism.

How is postsurgical hypothyroidism treated?

Postsurgical hypothyroidism is treated with thyroid hormone replacement therapy.