hyperirritable and combative, which can precipitate accidents or even assaultive behaviour. in more extreme cases features of psychosis, with delusions of persecution or delusions of reference, and pressure of speech may present themselves. rarely, patients develop visual or auditory hallucinations or a frank psychosis, and may appear schizophrenic, lose touch with reality and become delirious, such psychotic symptoms may not completely clear up after the hyperthyroidism has been treated. paranoia and paranoid-hallucinatory psychosis in hyperthyroidism usually have a manic disposition and it is therefore often not clear if the patient is experiencing a paranoid psychosis with depressive streaks, or a depression that has paranoid streaks. treatment of hyperthyroidism typically leads to improvement in cognitive and behavioral impairments. agitation, inattention, and frontal lobe impairment may improve more rapidly than other cognitive functions. however, several studies confirm that a substantial proportion of patients with hyperthyroidism have psychiatric disorders or mental symptoms and decreased quality of life even after successful treatment of their hyperthyroidism. effects on pre-existing psychiatric disorders patients with pre-existing psychiatric disorders, will experience a worsening of their usual symptoms, as observed by several studies. a study of 1999 found that graves' disease exacerbated the symptoms of tourette's disorder and attention-deficit hyperactivity disorder (adhd), and points out that the lack of diagnosis of the graves' disease compromised the efficacy of the treatment of these disorders. patients who are known to have a convulsive disorder may become more difficult to control with the usual medications, and seizures may appear in patients who have never previously manifested such symptoms. sub-clinical hyperthyroidism in sub-clinical hyperthyroidism, serum tsh is abnormally low, but t4- and t3-levels fall within laboratory reference ranges. it primarily affects the skeleton and the cardiovascular system (abnormalities in other systems have also been reported), in a similar but less severe and less frequent way than overt hyperthyroidism does. it can alter cardiac function, with increased heart rate, increased left ventricular mass index, increased cardiac contractility, diastolic dysfunction, and induction of ectopic atrial beats. long-term mild excess of thyroid hormone can thus cause impaired cardiac reserve and exercise capacity. in a large population-based study of 2008, the odds of having poorer cognitive function were greater for sub-clinical hyperthyroidism than for stroke, diabetes mellitus, and parkinson's disease. sub-clinical hyperthyroidism might modestly increase the risk of cognitive impairment and dementia. a possible explanation for the mental symptoms of sub-clinical thyroid disease, might be found in the fact that the brain has among the highest expression of thr's, and that neurons are often more sensitive than other tissues to thyroid abnormalities, including sub-clinical hyperthyroidism and thyrotoxicosis. in a 1996 survey study respondents reported a significant decline in memory, attention, planning, and overall productivity from the period 2 years prior to graves' symptoms onset to the period when hyperthyroid. also, hypersensitivity of the central nervous system to low-grade hyperthyroidism can result in an anxiety disorder before other graves' disease symptoms emerge. e.g., panic disorder has been reported to precede graves' hyperthyroidism by 4 to 5 years in some cases, although it is not known how frequently this occurs. however, while clinical hyperthyroidism is associated with frank neuropsychological and affective alterations, the occurrence of these alterations and their treatment in mild and sub-clinical hyperthyroidism remains a controversial issue. regardless of the inconsistent findings, a 2007 study by andersen et al. states that the distinction between sub-clinical and overt thyroid disease is in any case somewhat arbitrary. sub-clinical hyperthyroidism has been reported in 63% of euthyroid graves' disease, but only in 4% of cases where graves' disease was in remission. children and adolescents hyperthyroidism has unique effects in children on growth and pubertal development, e.g. causing epiphyseal maturation. in growing children, accelerated bone growth from hyperthyroidism can increase osteogenesis in the short term, but generally results in short-stature adults compared with the predicted heights. pubertal development tends to be delayed, or slowed. girls who have undergone menarche may develop secondary amenorrhea. hyperthyroidism is associated with high sex hormone-binding globulin (shbg), which may result in high serum estradiol levels in girls and testosterone levels in boys. however, unbound or free levels of these hormones are decreased. hyperthyroidism before the age of four may cause neurodevelopmental delay. a study by segni et al. suggests that permanent brain damage can occur as a result of the illness. ophthalmopatic findings are more common but less severe in children (severe infiltrative exophthalmos is virtually unknown before mid-adolescence), but besides that, many of the typical clinical features of hyperthyroidism in children and adolescents are similar to those in adults. an important difference between children and adults with graves' disease, is that children have not yet developed like adults have (psychological and physiological), and that they are a lot more dependent on their environment. the encephalopathy will have profound effects on children's developing personalities and developing relationship with their environment. disturbments in bodily development further complicates matters. the consequences for the development and the somatic and psychological well-being of the child can be very radical and sometimes irreversible. the earlier a person is affected by thyroid disease, the more the development of personality is affected and the bigger the delay from their potential development level. the child gets behind in its cognitive, emotional and sexual growth, which, by itself, also influences its processing abilities of the endocrine disease. children with hyperthyroidism tend to have greater mood swings and disturbances of behavior, as compared with adults. their attention span decreases, they are usually hyperactive and distractible, they sleep poorly, and their school performance deteriorates. because devastating personality and emotional changes often appear in the child or adolescent with graves' disease, many hyperthyroid children are (similar to many adults) referred to a developmental specialist or child psychiatrist before the presence of hyperthyroidism is suspected. older patients in older patients, emotional instability may be less evident, or depression may occur, and the symptoms and signs are manifestly circulatory. in many, the thyroid is not readily palpable. symptoms such as rapid heart rate, shortness of breath on exertion, and edema may predominate. older patients also tend to have more weight loss and less of an increase in appetite. thus anorexia in this group is fairly frequent, as is constipation. elderly patients may have what is called "apathetic thyrotoxicosis", a state in which they have less and less severe symptoms, except for weakness, depression and lethargy (making it even more prone to escape diagnosis). graves' disease and work considering the many signs and symptoms, the generally delayed diagnosis, and the possibility of residual complaints after treatment, it is little wonder that a significant number of people with graves' disease have difficulty keeping their job. one study found that of 303 patients successfully treated for hyperthyroidism (77% had graves' disease) 53% dealt with lack of energy. about one-third were unable to resume their customary work, mainly due to persistent mental problems. in their 1986 study of 26 patients (10 years after successful treatment of hyperthyroidism), perrild et al. note that four patients had been granted disability pensions on the basis of intellectual dysfunction. between 2006 and 2008, ponto et al. surveyed 250 graves' disease patients. of these, 36% were written off sick and 5% even had to take early retirement. in the same study, 34% of 400 questioned physicians reported treating patients with fully impaired earning capacity. patients can and do recover with appropriate therapy while continuing to work, but more rapid and certain progress is made if a period away from the usual occupation can be provided. two important considerations are adequate rest and attention to nutrition.