Hypothyroidism
Hypothyroidism is the disease state in humans and animals caused by insufficient production of thyroid hormone by the thyroid gland. It affects about 5% of the United Kingdom population over 60 years of age. As of 2006, more than 1% of the United Kingdom population were receiving T4 (Thyroxine) replacement therapy for hypothyroidism.
There are several distinct causes for chronic hypothyroidism. Historically and, still, in many developing countries iodine deficiency is the most common cause of hypothyroidism world-wide. In present day developed countries, however, hypothyroidism is mostly caused by Hashimoto's thyroiditis, or by a lack of the thyroid gland or a deficiency of hormones from either the hypothalamus or the pituitary.
Hypothyroidism can also result from sporadic inheritance, sometimes autosomal recessive. It is a relatively common disease in purebred domestic dogs as well, and can have a hereditary basis in dogs
Temporary hypothyroidism can be due to the Wolff-Chaikoff effect.
General psychological associations
Hypothyroidism can be caused by lithium-based mood stabilizers used to treat bipolar disorder (previously known as manic depression).
In addition, patients with hypothyroidism and psychiatric symptoms may be diagnosed with
* atypical depression (which may present as dysthymia)
* bipolar spectrum syndrome (including bipolar I or bipolar II disorder, cyclothymia, or premenstrual syndrome)
* borderline personality disorder
* a psychotic disorder (typically, paranoid schizophrenia)
* inattentive ADHD or sluggish cognitive tempo