Who knows the significance of this observation until much more investigation has been done? Maybe it is an artefact of some sort.
It does provoke questions such as: Why do thyroid glands vary in size significantly? Do we need larger thyroid glands in order to continue to produce enough thyroid hormone even when demand is high?
Prim Care Companion CNS Disord. 2015; 17(4): 10.4088/PCC.15l01778.
Published online 2015 Aug 20. doi: 10.4088/PCC.15l01778
PMCID: PMC4664570
Thyroid Gland Volume Is Significantly Smaller in Patients With Psychiatric Disorders Than in Those Without Psychiatric Disorders
Hidetaka Hamasaki, MD
Masafumi Kakei, MD, PhD
Hidekatsu Yanai, MD, PhD
Department of Internal Medicine, National Center for Global Health and Medicine Kohnodai Hospital, Chiba (Drs Hamasaki and Yanai); General Internal Medicine, Community Healthcare Studies, Jichi Medical University Graduate School, Tochigi (Drs Hamasaki and Kakei), Japan
To the Editor: The thyroid gland normally secretes thyroxine and triiodothyronine. A previous study reported that partial substitution of triiodothyronine for thyroxine improved mood and neuropsychological functions in hypothyroid patients treated with only thyroxine,1 suggesting an importance of the integrity of the thyroid gland for neuropsychological functions. It is clear that thyroid hormone plays an important role in the brain, influencing mood and cognition; however, the detail mechanisms remain to be elucidated. Here, we investigated the differences of thyroid gland volume, thyroid hormones, and thyroid autoantibodies between individuals with and without psychiatric disorders.
Full paper (though it is very short) available here:
If they have excluded those with autoimmune thyroid diseases why measure the antibodies? They must have measured them in the first place to establish who had autoimmune thyroid disease.
If they excluded patients taking lithium, how did they then diagnose psychiatric disorders?
Interesting proposal though .. a smaller gland may pose a higher risk of psychiatric disorder. What about those of us who have no thyroid left at all due to Hashi attacks?
Although we tend to think of antibodies being unique to autoimmune thyroid disease, you can have them after any form of trauma to the thyroid. Also, determination of antibodies might have revealed something like a correlation between undiagnosed autoimmune thyroid disease and psychiatric disorder.
Perhaps no thyroid does have impacts beyond the obvious?
Flo, they had to measure antibodies in order to exclude subjects with positive antibodies.
Diagnosis isn't dependent on treatment with Lithium. Lithium induced hypothyroidism is common which is why Lithium treated subjects were excluded.
I've had bipolar disease since my teens but I've no idea whether my thyroid was smaller than average. Thyroidless hasn't caused any mental deterioration that I'm aware of. On T4+T3 my FT4 and FT3 are very similar to pre-thyroidectomy although my TSH is very suppressed.
I think these should be tested after being born as it was so said they don't know why this happens. Is it a virus? Certain strain of influenza or chicken box or what? Is it something you born with and why.
And which was first chicken or egg? How long it takes to develop?
Helvella, Interesting that significantly smaller thyroids didn't affect serum TSH, FT4 and FT3 levels and that levels and positive autoimmunity were the same in those with and without psychiatric illness.
I thought it was very sensitive to describe "completed suicide" rather than "successful suicide".
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Patient info post on thyroid disorder 
Thyroid dosage Less than 100mg without a thyroid
