Do Thyroid Replacement Hormones Relieve Symptoms of Depression?

Depression is a common mental disorder experienced by people of all genders and ages. It is marked by a recurrent down mood, lack of desire to engage in new or old activities, changes in appetite, changes in sleep schedule, and withdrawal from friends and family. Depression, unlike some illnesses, does not have a single cause, so people with depression may be suffering for many reasons. Many people have depression due to a psychological reason, but there are some people whose depression originates with a chemical imbalance in the body.

A lot of the research has looked neurotransmitters, which are chemicals that the nervous system uses to allow neurons to communicate. Recently, scientists have begun to look at other physiological reasons, particularly in the endocrine system. One hormone, a chemical messenger employed by the endocrine system, is a thyroid hormone that is produced by the thyroid gland. The thyroid gland is a butterfly-shaped gland found slightly above the sternum. Thyroid hormone refers to two separate hormones that are interconverted in the body, triiodothyronine (T3) and thyroxine (T4).

As with most organs, the thyroid gland can stop functioning. When it works below the physiological level a person needs to maintain a healthy metabolism, one is said to have hypothyroidism. This condition is marked by cold sensitivity, weight gain, hoarseness, and a slower heart rate. Those experiencing hypothyroidism are also likely to have fatigue, excessive sleepiness, and problems concentrating on tasks. These symptoms, especially the ones associated with sleep, activity, and energy, can all feed directly into depression. This leaves depression as a somewhat common symptom people may experience with hypothyroidism.

In hypothyroidism, the thyroid stops responding to hormonal signals from the pituitary gland in the brain, causing it to produce less thyroid hormone. Hypothyroidism is a common disorder found throughout the United States. Although men can develop it, hypothyroidism is much more prevalent in women, and the incidence increases with age. Although some symptoms overlap, researchers still do not understand exactly why and how hypothyroidism and depression are linked. Regardless, many people who are being treated for hypothyroidism are also taking antidepressants, making a clear link between the two.

One treatment for hypothyroidism is thyroid hormone replacement, which adds more thyroid hormone to the body usually in the form of T3. The increase in thyroid hormone helps alleviate the symptoms of a low functioning thyroid gland. This can also help to reduce symptoms of depression because the body has a more natural level of thyroid hormone to aid in the body’s biological activities. Levothyroxine is another sort of thyroid hormone replacement treatment that uses T4 instead of T3, but the effect of this treatment is the same as the two forms interconvert depending on their location in the body.

While hypothyroidism provides a logical bridge to depression, some people who do not have hypothyroidism benefit greatly from antidepressant drugs being mixed with thyroid hormone replacement. Ultimately, this means that hypothyroidism is sufficient but not necessary for depression. The idea of mixing antidepressants and thyroid hormone replacement does come from the commonalities of the symptoms of depression and hypothyroidism. Thyroid hormone replacement can be used with most antidepressants, and thyroid hormone replacement even seems to increase how quickly tricyclic antidepressants work when the two are started together.

At this point, researchers are still uncertain as to why thyroid hormone replacement works with antidepressants, but it is being studied. One common theory is that the thyroid hormone and the antidepressant, once taken, interact together in the brain. The thyroid hormone may somehow enhance the effect of antidepressants to alleviate the symptoms of depression. Some researchers approach this treatment from a different school of thought. These scientists theorize that antidepressants and thyroid hormone work independently of each other in the brain. They believe that thyroid hormone helps improve mood and concentration while antidepressants carry out their expected effects.

Because of how common depression is, it is important for psychologists and other experts to study it and what can help those who suffer from it. Research has led to places all over the body, ranging from the brain to the gut to the thyroid gland. Hypothyroidism has many symptoms that overlap with depression, which caused some scientists to believe that thyroid hormone replacement might help. After trials, it was found that thyroid hormone replacement is sometimes effective, even for people who do not have hypothyroidism. Ultimately, thyroid hormone replacement appears to be an effective treatment for depression when prescribed with antidepressants.

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