Discussion
The patient who inspired this case review, is an 81-year-old seemingly healthy female, sensory processing and usual behavior were suddenly altered. This lasted for a short period of time, with constant fluctuations, showing symptoms of memory impairment, disorientation and language impairment, as stated by the patient. The patient requested a consultation after an episode of unusual behaviors that had started suddenly and developed in a 3-day period. As far as she can remember and as confirmed by her neighbor, she seemed disorganized, leaving her activities unfinished for no apparent reason and forgetting to resume them, showing significant memory loss (she could not remember who her neighbors were, people who she has known for decades), a potential inversion of the sleep cycle, wakefulness and a state of confusion. All these symptoms fluctuated and were not considered to be related to any other cognitive disorder.
Although during that period the patient appeared to be in a state that would fall under psychotic, she actually presented a rather typical case of delirium in accordance with the DSM-5 criteria for delirium. There is a set of criteria that is difficult to detect: family history, medical exams or analyses that suggest the episode is a direct physiological consequence of a condition, intoxication or withdrawal syndrome, or the exposure to a certain toxin (or a combination thereof).2 Symptoms described may resemble catatonia, but she only was having agitation no influenced by external stimuli, and the diagnostic criteria for catatonia needs three (or more) symptoms of catatonia.
During the actual interview, the patient was feeling better. The results of her medical exam were within the expected limits. Her mental assessment only revealed a slight difficulty with calculations, a new MMSE practiced showed a score of 27 points. The patient is a known carrier of hyperthyroidism and normally takes her medication on a daily basis. This treatment was interrupted abruptly, as she forgot to take her medication and, within 10 days, started to show the above-mentioned symptoms, which can be attributed to the seven-day half-life of levothyroxine. The thyroid-stimulating hormone and Thyroxine libre lab tests could not be performed because the patient attended the next consultation after she resumed her medication. That resuming the consumption of levothyroxine made her symptoms disappear supports the diagnosis of delirium caused by the sudden interruption of the treatment.
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The sudden interruption of the chronic levothyroxine treatment triggered delirium symptoms, of which stress was the main trigger. The relationship between delirium and medication withdrawal was made more apparent due to the fast disappearance of the symptoms once the treatment was resumed.
Literature defines thyroid hormones as responsible for regulating the metabolism.8 A decrease in the level of thyroid hormones produces significant changes in the receptors of noradrenaline, serotonin, and GABAergic agents, but its psychiatric illness-producing mechanism is not clear.9 Accordingly, altering one of these neurotransmitters, in addition to variations of the thyroid hormone may cause delirium, as alterations in the function of neurotransmitters have been described, among others, as the physiopathological cause of delirium.10,11
The onset of symptoms caused by the sudden interruption of the levothyroxine treatment evidences that the decrease in thyroid hormone levels in the patient, in addition to her reduced capacity to cope with change and stressors common of her age, may have been the cause of delirium, which may reappear should the treatment be interrupted yet again.
