Sanesco Blog

Can Your Thyroid Make You Smile?


Think about all of the things that make you smile. Your family or a nice vacation may do the trick. But, you may have forgotten one important thing…

Studies have found that an adequately functioning thyroid gland supports optimal serotonin synthesis, thus, making us happier.

Depression and Hypothyroidism

Serotonin (5-HT) is an inhibitory neurotransmitter that functions to combat depressive moods and promote happiness. Additionally, depression has been associated with decreased serotonin levels, as well as hypothyroidism. Hypothyroidism is simply decreased activity of the thyroid gland.

To connect these links to find if hypothyroidism influences serotonin levels, studies have tested the influence of experimentally induced hypothyroidism in rats.

Hypothyroidism and Serotonin

When adult animals were induced into hypothyroid states, 5-HT turnover in the brainstem was increased (the amount of time 5-HT was available for use was shorter), and cortical 5-HT concentrations were decreased.

Furthermore, when thyroid hormones were administered to these same mice, results demonstrated increased 5-HT concentrations and through a chain of events, more cortical and hippocampal 5-HT release.

There is also some suggestive evidence that thyroid hormones can up-regulate cortical 5-HT2 receptor sensitivity, leading to more serotonin function.

Balancing Serotonin and Thyroid Function

These increases in serotonin neurotransmission can result in happier and more balanced moods. So the next time you find yourself unable to obtain a smile, it may just be your thyroid telling you that it needs a little boost.

Symptoms of Hypothyroidism

Typical signs that a person might be hypothyroid include:

  • cold extremities
  • decreased stamina and feelings of fatigue
  • low libido
  • poor memory
  • constipation
  • depressive moods

among several other symptoms. A person with a poorly functioning thyroid may also experience hair loss or dry, brittle hair.


The best way to find out if your thyroid is functioning optimally is to visit your practitioner.



Bauer M, Heinz A, and Whybrow PC. 2002. Thyroid hormones, serotonin and mood: of synergy and significance in the adult brain. Mol Psychiatry. 7(2):140-56.

Rahman, MH and Ali, MY. 2014. The Relationship between Thyroid Hormones and the Brain Serotonin (5-Ht) System and Mood: Of Synergy and Significance in the Adult Brain – A Review. Faridpur Med. Coll. J. 9(2): 98-101.

Clinical Contributor

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Ramona Richard, MS, NC

Ramona Richard, MS, NC

Ramona Richard graduated with honors from the University of California with a Bachelor’s Degree in psychology and graduated summa cum laude with a Master’s Degree in Health and Nutrition Education. She also holds a Standard Designated Teaching Credential from the State of California, is a California state-certified Nutrition Consultant and a member of the National Association of Nutrition Professionals.

Ramona has participated in nutrition education in both public and private venues, including high school and college presentations, radio and public speaking for the past 20 years. She is the owner of Radiance, a nutrition consulting company, the Director of Education for Sanesco International, and a medical technical writer.

Disclaimer: The information provided is only intended to be general educational information to the public. It does not constitute medical advice. If you have specific questions about any medical matter or if you are suffering from any medical condition, you should consult your doctor or other professional healthcare provider.

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Inhibitory Neurotransmitter


One of our feel-good neurotransmitters; Low levels of serotonin may relate to occasional symptoms like moodiness, sleep issues, and carb cravings. 

Learn why and how to test serotonin levels