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Replacing T3 During Severe Stress or Illness—Necessary or Not?

The issue of supplementing for a low thyroid hormone level during acute illness or severe stress has been debated among endocrine experts but now appears unnecessary given the most recent analysis of the research.

With Matthew Maiden, PhD, and Robert .J. McConnell, MD

When you're healthy, your thyroid gland just hums along, keeping up with its many important functions—As you likely know, it produces hormones that regulate your metabolism, including assuring heart health, digestive function, muscle control, mood, and bone strength.1

Debate about T3 supplementation during stress or severe illness is overblown.The controversy swirling around T3 supplementation during acute stress and severe fatigue does not appear beneficial. Photo: 123rf

Fatigue may be a common symptom in patients experiencing thyroid diseases, as well as conditions such a chronic fatigue syndrome and cancer. Fatigue also may arise in conditions as diverse as starvation as well as surgical stress and post-surgical recovery.2 This may be easily explained given the role of the hypothalamic-pituitary-thyroid axis responsible for regulating the body’s physiologic energy functions.

However, when you are faced with a severe illness, all the essential functions under the control of the thyroid can go haywire.2 The resulting condition is called by various names—sick euthyroid syndrome, low T3 syndrome, or non-thyroidal illness syndrome. And this is not to be confused with hypothyroidism, which occurs when the thyroid-stimulating hormone (TSH), or thyrotropin, rises while levels of T3 and T4 remain low.

Experts have long debated what to do when the thyroid shuts down or malfunctions temporarily—do they intercede to replace hormones or to let it be, reasoning that the abnormalities may be an adaptive and temporary response to the illness. To shed light on this thyroid failure, Australian doctors reviewed what is known about the debate about whether treatment with thyroid replacement hormone is beneficial or not.3

First, it helps to know how the condition arises. "Thyroid hormone levels change during illness," says Matthew Maiden, PhD, FCICM, FACEM, a researcher from the Royal Adelaide Hospital in Adelaide, South Australia, co-author of the report.3  "In particular, the most biologically active form of thyroid hormone—Triiodothyronine, or T3, falls. This is a consistent phenomenon noted across all types of illness, for example, infection, heart attack, trauma, even cancer," he says.

How far the level of T3 falls is most likely related to the severity of the illness, he tells EndocrineWeb, ''and is most noticeable in patients requiring treatment in the intensive care unit (ICU)."3

Severe Fatigue and Physical Stress Most Closely Linked to Low T3  

Research on patients, both adults and children, who are undergoing heart surgery (ie, cardiac bypass) has examined the apparent increased likelihood of fluctuations in thyroid hormone levels since these hormones have a direct impact on cardiac function.4.5 In fact, people facing a critical illness, starvation, cancer, in addition to major surgery, may experience a dip in their normal T3 levels.

In particular, hypothyroidism has been linked to a decline in cardiac performance and possible role in atrial fibrillation. Similarly, the impact of T3 status has been reported on several other clinical conditions, specifically during the perioperative period.6,7 Low serum T3 levels have been reversed with supplemental T3, and has also been shown to improve hemodynamic performance and reduce arrhtymias.5

This state in which normal thyroid function is adversely affected appears to affect even people with chronic fatigue syndrome have been noted to experience low T3 syndrome.8

Thyroid Hormone Replacement Debated in Times of Stress, Illness

"Given that T3 is required for health, it remains unclear if a low T3 level as observed during a severe illness is an adaptive response or if a lack of this hormone contributes to poor recovery from critical condition," Dr. Maiden says. "Many endocrinologists believe this low T3 state does not require treatment." But the uncertainty on that point of view continues to circulate, he says, possibly because there isn’t enough research on the topic to properly inform doctors.

In this paper,3 Dr. Maiden reports on studies that have experimented with supplementation of T3 in different scenarios. For instance, in one study of 23 heart transplant candidates who received T3 replacement suggested increased heart output without causing any bad side effects.7 In another study, 20 patients with dilated cardiomyopathy, another heart condition, who received T3 hormone replacement to bring their thyroid levels to a normal range seemed to result in good effects.5

In other diseases, including those affecting the kidney, the replacement seemed to make no difference,9  according to the authors.

With such mixed results—some research suggesting benefit and other studies not, Dr. Maiden says the jury is still out on whether there is any advantage or benefit to providing patients with T3 hormone replacement when they are critically ill. Unfortunately, there is a need for more and bigger studies, he says, and he encourages those who are hospitalized (ie, intensive care, critical care, or cardiac care) and their families to consider joining a clinical trial that addresses whether T3 hormone replacement offers any benefit or not, if that becomes an option for them.

Experts Say Focus on Recovery from the Illness, Not T3 Status

Robert McConnell, MD, professor of medicine at Columbia University Medical Center, New York, and medical director of the Thyroid Center there, reviewed the report and put it into perspective.  He says that the report ''is yet another of many review articles that have concluded that 'the place of restoring T3 levels in critical illness continues to remain uncertain.'"

"A great majority of clinical endocrinologists believe that the fall in circulating T3 during critical illness is a physiologic alteration that should not be disrupted with T3 replacement," he tells EndocrineWeb.  Many experts agree with that, saying the decrease in T3 is most likely just the body's adaptive response to conserve energy during the healing process.

Dr. McConnell continues: "Although relatively low doses of T3 have shown no consistent harm, they haven't demonstrated any survival benefit either."

In his opinion, "if a therapy has little or no upside benefit but has a potential downside harm, then it should not be used."

While available forms of synthetic T3, or liothyronine (eg, Cytomel and Triostat) are an option forthis patient population, most patients in need of supplemental T3 will most likely receive T3 intravenously while the patient is in the hospital recovering from surgery or being cared for in the ICU or CCU unit.

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