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Hypothyroidism and Depression Connection

Thyroid Advisor

April 17, 2018

Fact Checked

Last Updated on December 21, 2021

Depression is not just a persistent feeling of sadness; it is a serious health condition indicated by symptoms affecting both mental and physical health and wellbeing. People develop depression due to all sorts of reasons.

Sometimes the underlying health problem can lead to depression, but in other instances, this illness can increase the risk of developing some disease or condition. You’ve probably heard or read that depression is associated with thyroid problems, particularly hypothyroidism.

Is that true?

This post explores the potential connection between depression and hypothyroidism.

How common is depression?

Depression is more prevalent than we think. According to the National Institute of Mental Health, about 16.2 million American adults or 6.7% of this population had at least one major depressive episode in 2016. Figures also show that depression is more prevalent in adult women than men with ratio 8.5% vs. 4.8% respectively[i].

In October 2017, Goodwin R. et al published a study which revealed that depression appears to be increasing among Americans, especially among youth. Findings demonstrate that depression increased significantly among people in the US from 2005 to 2015 from 6.6% to 7.3%[ii].

Rates of depression could be even higher than estimates show. Official statistics only take into account diagnosed cases of depression, but there are many people who don’t seek medical assistance for symptoms they experience and hence receive no diagnosis.

Both more prevalent in women

As seen above, statistics show that depression is more common in women than men and studies support that. For instance, a study about gender differences in depression and anxiety, based on the Netherlands population, found that women reported a younger age of onset of single and recurrent major depressive disorder (MDD) than men. Women also experienced higher rates of anxiety, but they had a lower alcohol use than male counterparts[iii].

A research from the Psychological Bulletin demonstrated that twice as many women as men were affected by depression. The most concerning finding was that gender differences in the prevalence of depression were already present at age 12 and hormonal changes may have something to do with it[iv].

Why is gender prevalence of depression so important? The answer is because hypothyroidism is also more prevalent among women than in men. Carle A. et al carried out a study to examine gender-specific symptom prevalence of hypothyroidism in the Danish population.

Scientists found that healthy women were significantly more likely than normal men to report symptoms of hypothyroidism[v]. Evidence shows that hypothyroidism is six times more common in women than it is in men[vi].

A greater prevalence in women than in men is what both depression and hypothyroidism have in common. This could also indicate a stronger relationship between two conditions which will be discussed below.

Are depression and hypothyroidism really connected?

For many years it was debated whether depression and hypothyroidism are, indeed, connected to one another. Many studies have been conducted on this subject, but they yielded different results. The reality is that we will need more research on the relationship between hypothyroidism and depression to understand the underlying mechanisms and learn more about both conditions.

For instance, Kim J.S. et al found no apparent association between subclinical hypothyroidism and incident depressive symptoms in middle-aged men and women[vii]. On the other hand, Jain L. et al conducted a study to evaluate the correlation of depression in female hypothyroid patients and found a strong relationship between the two. The research showed that the prevalence of hypothyroidism in depressed subjects was 20%.

The prevalence of depression in hypothyroid patients was 36.67%. Subclinical hypothyroidism was more prevalent than clinical hypothyroidism with a ratio of 13.3% vs. 6.7% respectively. Scientists concluded that depression and hypothyroidism have a strong relationship[viii].

Hypothyroid patients frequently experience problems such as apathy, depression, psychomotor slowing, and cognitive dysfunction. What’s more, patients with severe form of hypothyroidism often exhibit clinical symptoms that are strongly similar to those of melancholic depression and dementia.

Depression and other mood disorders are linked to several thyroid abnormalities. These abnormalities usually involve elevated T4, positive thyroid antibodies, low T3, increased rT3 (reverse T3), and weakened TSH response to TRH, thus suggesting a unique condition where a person’s brain is in hypothyroidism state while the body itself exhibits systemic euthyroidism.

Various factors could be behind this unusual state. Possible explanations include transport of thyroid hormone and uptake in the brain and neuronal cells, but thyroid hormone receptor defects could also be to blame[ix].

Depression and thyroid hormones

Although many studies inspected the relationship between depression and thyroid hormones, this subject is still poorly elucidated. The involvement of hypothalamic-pituitary-thyroid (HPT) axis in the pathogenesis of depression is supported by various studies. While some research shows the normal range of thyroid hormone levels during a depressive episode, the great deal of evidence confirms the diverse changes in different hormones linked with this axis.

Regarding TSH some studies report increase while others claim its levels decrease during a depressive episode. Concerning T3 the evidence is more conclusive and it shows the levels of this hormone tend to reduce in the presence of depression. In fact, the degree of T3 reduction is associated with severity of depression.

Don’t forget that hypothyroidism is a condition indicated by lower or insufficient production of thyroid hormones. When it comes to T4, results are still contradictory due to a diversity of factors such as differences in phenotypes of depressive patients, severity and duration of disease, and many others[x].

It is also important to mention that “thyroid hormones influence noradrenergic and serotonergic neurotransmission which” are crucial “in the pathogenesis of depression” and they also pose as targets for treatment of this condition. Studies show that administration of T3 leads to an increase in “serotonin levels in the cerebral cortex.” At the same time, hypothyroidism is linked with lower levels of serotonin.

This neurotransmitter also has an inhibitory impact on TRH secretion, thus suggesting the potential existence of a feedback loop which allows activation of HPT axis when levels of serotonin are low[xi]. As a reminder, serotonin is a neurotransmitter known as a “happy chemical” because it contributes to good mood, wellbeing, appetite, and even sleep.

They share some symptoms

As demonstrated above, depression and hypothyroidism are connected in many ways, but it is a little-known fact that they have some other things in common. Did you know that symptoms of depression and hypothyroidism are similar too? Let’s check it out.

The table above shows that not only hypothyroidism and depression have some symptoms in common, but depression is also a symptom of an underactive thyroid gland.

Antidepressants and hypothyroidism

Treatment of depression usually revolves around the use of antidepressants together with therapy sessions. The latter help patients get to the bottom of their problems in order to understand why they feel in a certain manner and how they can get better, deal with difficult times, among other things.

Since we’re talking about hypothyroidism and depression it’s impossible not to wonder whether antidepressants have a positive or negative impact on your thyroid condition.

De Carvalho G. A. et al found that neither sertraline nor fluoxetine was linked to clinically noteworthy alterations in function of thyroid gland and thyroid autoimmunity in either euthyroid or primary hypothyroid patients with depression. Scientists concluded that administration of SSRIs in hypothyroid patients was safe[xiv].

Evidence points to normalization of pretreatment thyroid function tests, primarily T4 levels, with remission of depression. Both SSRIs and tricyclic antidepressants appear to amplify the activity of deiodinase enzyme type 2 (D2) thereby leading to the enhanced conversion of T4 in active T3 in the brain.

Antidepressants with various mechanisms of action have a different impact on thyroid.

Hypothyroidism treatment and depression

Hypothyroidism requires adequate management and to make it happen, your doctor will probably prescribe thyroid hormone replacement therapy i.e. you’d have to take levothyroxine, a synthetic form of hormone T4. It’s not uncommon for patients to be in the poor mood while taking medications for hypothyroidism.

Studies show that subjects on thyroxine have poorer psychological wellbeing than their healthy counterparts with no thyroid diseases and it only confirms the relationship between hypothyroidism and depression.

Reasons, why hypothyroid patients may have a poor wellbeing due to thyroxine, are numerous and a possible explanation is the misattribution of symptoms. Both depression and hypothyroidism are common, particularly in older women, and there is a reasonable prevalence of overlap of two conditions.

It is recommended for doctors to check thyroid status of their patients with depression. Sometimes, the lack of understanding the causes of certain symptoms can impair the treatment and weaken psychological wellbeing of a patient.

It’s also important to mention that supplementation with T3 could accelerate the clinical response to antidepressants, but more research is needed on this topic.

Menopause

Menopause is an inevitable part of a woman’s life, it’s a transition that you need to enter and one can’t really avoid it. The average age of onset of menopause among American women is 51. Why are we talking about it in this article?

It’s simple, both hypothyroidism and depression are more prevalent in women than men and both conditions are particularly common after menopause. Marsh W.K. et al found that women are more vulnerable to depressive symptoms during and after menopause transition due to fluctuating hormone changes.

Women who enter menopause transition earlier have a higher risk of developing depression[xv].

Hypothyroidism is more common in middle-aged and older women than in younger females. This is also the time when women are either approaching or they have gone through a menopause transition. Of course, estrogen fluctuations could be to blame.

Santin A.P. et al examined the influence of estrogen on thyroid receptors. They found that estrogen levels could affect thyroid function and contribute to thyroid disorders[xvi]. Of course, more research is needed to elucidate the relationship between thyroid and estrogen.

Depression management tips

Having both hypothyroidism and depression is not easy, but there are many ways you can manage it. Consult your doctor about symptoms you experience and find out how you can manage depression if you’re taking medications for thyroid disorder and vice versa.

Even if you aren’t diagnosed with depression, you may ask your doctor about this because two conditions are strongly related. Simple lifestyle tweaks can help you feel better and improve your mood. For example:

• Get enough sleep
• Exercise and stay physically active
• Eat a healthy diet
• Adopt a positive outline, challenge negative thoughts
• Talk to a therapist
• Try a new hobby
• Meditate
• Practice yoga

Conclusion

Both hypothyroidism and depression are common conditions and they have numerous things in common.

They are more prevalent in women, especially during menopause time, and they share some symptoms. Bearing in mind that relationship between two conditions is strong, it is important to stay informed, consult your doctor, and have a proactive approach to the subject.

References