https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2679767?utm_source=silverchair&utm_campaign=jama_network&utm_content=weekly_highlights&cmp=1&utm_medium=email

In a nutshell, if you are depressed or anxious, be sure to have a screen for autoimmune thyroiditis (the overwhelming cause of hypothyroidism in the population).

The authors conclude: “Taking as a basis a general 12-month prevalence for depression of 6.6%5,6 and a general 12-month prevalence for anxiety disorders of 18.1%6 in the United States, we conclude with ORs of 3.56 (depression) and 2.32 (anxiety) that approximately 23.8% of patients with AIT experience depression and approximately 41.6% of patients with AIT experience anxiety disorders. That implies that 3% of the US population (approximately 9.7 million people) has depression and 5.4% of the US population (approximately 17.5 million people) has anxiety disorders concomitantly with AIT. Thus, 45.5% of depressive disorders and 29.8% of anxiety disorders are associated with this endocrine disease.” (my italics)

“This test must not be narrowed down to thyrotropin levels and free triiodothyronine and free thyroxine but should comprise thyroid peroxidase antibodies as well”

“Regarding pharmacotherapy, an extension of possible medication must be taken into consideration. Besides typical levothyroxine treatment, selenium supplementation can help to reduce the amount of thyroid antibodies and improve mood or well-being.⁷⁶ Furthermore, an early administration of antidepressants could be indicated to attenuate the chronic course of AIT. Thyroid metabolism is associated with the brain serotonin system⁷⁷; thus, selective serotonin reuptake inhibitors are appropriate medications to treat depression in patients with AIT.⁷⁸ Classical, tricyclic antidepressants, however, are not suited for patients with hypothyroidism.”

Selenium study concludes”

“Conclusions: On the basis of the best available evidence, Se supplementation is associated with a significant decrease in TPOab titers at 3 months and with improvement in mood and/or general well-being. Evidence suggests a different pattern of response to Se supplementation in HT relative to baseline TPOab titers, and this, if confirmed, could be used to identify which patients would benefit most from treatment. An improvement in thyroid function and morphology should be demonstrated before Se routine supplementation can be recommended in the treatment of HT.” (Thyroid, Vol 20, No 10)

(Note: 2017 analyses and current opinions about selenium seem to agree that circulating antibodies normalize, but disagree how clinically relevant it might be; they disagree whether widespread use of selenium is justfied.  Low selenium levels are linked to AIT, and insufficiency apparently a cause, but not always so widespread use questioned)