Experiencing a shorter tempter, feeling overemotional, anxious and clingy or even wanting to be left alone are not uncommon with hormonal health conditions. We already know the mood swings caused by hormonal changes in menstruating women and those experiencing the menopause or perimenopause, are not uncommon. Hypothyroidism can lead to fluctuating levels of hormones too.
Why Hypothyroidism Can Cause Mood Swings
The thyroid plays a crucial part in brain chemistry and function, so we shouldn’t be surprised that a thyroid condition, such as hypothyroidism, can cause unpredictable mood swings.
An optimally treated thyroid condition should ideally leave us with little to no ongoing symptoms or complaints, such as mood swings and mental health difficulties. Therefore, if you’re still experiencing these whilst on thyroid medication, you may wish to confirm that you are indeed being optimally treated. Many of us don’t realise that our Free T3 levels, which are important for optimal functioning of the brain, including: cognitive function, the ability to concentrate, mood, memory, attention span, emotions, the ability to cope with life’s stresses etc. are actually low.
Unfortunately, a lot of us aren’t even having our Free T3 levels tested, to check if our thyroid medication is optimising thyroid hormone levels. Free T3 forms part of the full thyroid panel, with the the other test in this panel being: TSH, Free T4, Thyroid Peroxidase Antibodies and Thyroglobulin Antibodies where possible.
Most the time, it seems we’re only having TSH checked, which of course, didn’t give the full picture.
Only testing TSH does not confirm whether thyroid medications, and especially T4-only medications such as Levothyroxine, have adequately raised T3 and T4 levels. Especially as so many of us on T4-only medications struggle to convert the T4 in them to enough T3.
Many studies also conclude a link between low Free T3 levels and mood. In fact, suicidal patients have been found to have a higher incidence of thyroid disorders, with lower Free T3 levels than non-suicidal people. 
How Hashimoto’s Can Cause Mood Swings
Hyperthyroid symptoms can include hyperactivity, anxiety, irritability and disturbed sleep, whilst hypothyroidism often causes fatigue and depression. Do those swinging moods remind you of anything? Bipolar disorder perhaps?
It could well be suggested that some bipolar diagnoses are actually masking undiagnosed Hashimoto’s, where patients swing between hypo and hyper symptoms, as the thyroid is attacked and destroyed, and thyroid hormone is released into the bloodstream in waves. This can present as mood swings.
The 2002 study: “High Rate of Autoimmune Thyroiditis in Bipolar Disorder: Lack of Association with Lithium Exposure”, found that Hashimoto’s antibodies were more prevalent in a sample of outpatients with bipolar disorder (28%), in comparison to a control group (3-18%). 
Getting Hashimoto’s controlled i.e. in remission can help.
If you don’t know whether you fall in to the 90% with Hashimoto’s as the cause for your hypothyroidism, you can ask your doctor test, or order the test yourself from places such as LetsGetChecked (a worldwide testing company) and Medichecks (for those in the UK).
If You Still Need Medication for Your Mental Health, Then That’s OK Too
Of course, antidepressants, anti-anxiety meds etc. can be a great help to many people and taking them is not ‘wrong’. I am not anti-medication, but I am pro-informed decision, which means making sure those that who are thyroid patients also experiencing mental health conditions, know that addressing their endocrine health fully may well resolve their mental health complaints and mood swings which often affect relationships and wider parts of life.
Other Things To Consider
Being low in vitamins such as iron, B12 and Vitamin D can also affect our mood and mental health, as can other hormonal imbalances such as oestrogen dominance. Some thyroid patients also find that going gluten-free helps.