It has been known for years about the relationship of depression and low thyroid function. Not long after hypothyroidism was first identified officially in England in 1873, it was understood that mental disorders would accompany the condition. Psychiatric circles have utilized thyroid hormone in the past with great result, until the advent of newer psychotherapeutics took over.
The brain has multiple receptors for thyroid hormone. When thyroid hormone is low or high, it can cause an inability to focus and understand complex questions and tasks. Additionally, the psychological symptoms can range from mood swings, anxiety, and irritability to hallucinations and psychotic episodes. However, when a patient presents with hypothyroidism, depression may or may not be the most prominent feature. Or worse, if a patient presents with depression, the hypothyroidism may or may not be discovered, leading to the use of psychotropic drugs only without treating the underlying hypothyroid cause of the depression.
The use of T3 by psychiatrists has been noted to be effective for depression.(1) However, all too often, the dose would not be increased to a point of elimination of symptoms or at least for any consistent duration of time, leading to the additional need of psychotherapeutic drugs.
The key to helping with many cases of depression is to find a healthcare practitioner familiar with treating the underlying low metabolic state comprehensively while allowing for sufficient natural thyroid hormone dosing to be applied to the clinical situation. Full hormonal balance should be sought with attention to nutritional and lifestyle changes geared toward improving the metabolism.
(1) Whybrow PC, et. al. Thyroid function and the response of L-liothyronine in depression. Arch Gen Psychiatry 1972;26:242.