The hyperthyroid patient shows minor changes in emotions and mentation. Restlessness, irritability, apprehension, emotional lability, and at times even agitation and a generalized chorea may occur. Either of 2 trends may be observed in the relatively rare thyrotoxic patient who develops a psychosis. There may be a mild manic state, with its characteristic increase in psychomotor activity, excessive talkativeness, and flight of ideas, or there may be depression, with its somber mood, weeping, and anxiety. Visual and auditory hallucinations may be present in both groups. Usually there is something more than simple mania or agitated depression, that is, some clouding of the sensorium with perplexity and confusion, suggestive of delirium. The condition is said to be related to the premorbid personality, some personality types being more vulnerable, but this is disputed. It can be stated that the psychiatric changes are not directly related to the severity of the thyrotoxicosis. Treatment of the hyperthyroidism does not result in prompt arrest of the psychic disorder; recovery usually takes place over a period of months. One must distinguish this illness from other types of recurrent psychoses that happen to be coincidental with or precipitated by hyperthyroidism and from the steroid-responsive encephalopathy called “Hashimoto encephalopathy” mentioned below.
With myxedema there is a characteristic slowness and thickness of speech, drowsiness, hypothermia, mental dullness, listlessness and apathy, irritability, and sometimes suspiciousness. The patient may sleep most of the time, having to be awakened for meals. A disturbance of memory and the lack of genuine symptoms of depression, such as feelings of hopelessness and loss of self-esteem, help to distinguish the mental disorder of myxedema from that of a depressive illness. Nevertheless, unless one thinks of myxedema in cases of psychomotor retardation, the diagnosis will be missed. Reduced cerebral blood flow and metabolism have been found in myxedema; with specific therapy, these functions are restored to normal within 2 to 3 weeks.
An entirely different type of mental disturbance characterized by intermittent delirium and stupor often associated with myoclonus and autoimmune in nature may occur in patients with thyroiditis (“Hashimoto encephalopathy,” Chap. 39). The illness is responsive to glucocorticoids. The diagnosis is confirmed by the finding of circulating antibodies to thyroglobulin and thyroid peroxidase but there are high rates of false positive tests, particularly in middle-aged an older women.
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