Parkinson's disease camouflaging early signs of hypothyroidism

Thyroid Disorders and Movement Disorders-A Systematic Review

Background

There is overlap between movement disorders and neuroendocrine abnormalities.

Objectives and methods

To provide a systematic review on the association of thyroid dysfunction and movement disorders. Thyroid physiological function and classical thyroid disorders highlighting typical and atypical manifestations including movement disorders, as well as diagnostic procedures, and treatments are discussed.

Results

Hypothyroidism may be associated with hypokinetic and hyperkinetic disorders. There is debate whether their concomitance reflects a causal link, is coincidence, or the result of one unmasking the other. Hypothyroidism-associated parkinsonism may resemble idiopathic Parkinson's disease. Hypothyroidism-associated hyperkinetic disorders mainly occur in the context of steroid-responsive encephalopathy with autoimmune thyroiditis, that is, Hashimoto disease, mostly manifesting with tremor, myoclonus, and ataxia present in 28-80%, 42-65% and 33-65% in larger series. Congenital hypothyroidism manifesting with movement disorders, mostly chorea and dystonia, due to Mendelian genetic disease are rare.Hyperthyroidism on the other hand mostly manifests with hyperkinetic movement disorders, typically tremor (present in three quarters of patients). Chorea (present in about 2% of hyperthyroid patients), dystonia, myoclonus, ataxia and paroxysmal movement disorders, as well as parkinsonism have also been reported, with correlation between movement intensity and thyroid hormone levels.On a group level, studies on the role of thyroid dysfunction as a risk factor for the development of PD remain non-conclusive.

Conclusions

In view of the treatability of movement disorders associated with thyroid disease, accurate diagnosis is important. The pathophysiology remains poorly understood. More detailed case documentation and systematic studies, along with experimental studies are needed.

Alterations of thyroidal status in brain regions and hypothalamo-pituitary-blood-thyroid-axis associated with dopaminergic depletion in substantia nigra and ROS formation in different brain regions after MPTP treatment in adult male mice

MPTP produces oxidative stress, damages niagrostriatal dopaminergic neurons and develops Parkinsonism in rodents. Due to paucity of information, the thyroidal status in brain regions and peripheral tissues during different post-treatment days in MPTP-induced mice had been executed in the present study. MPTP depleted tyrosine hydroxylase protein expressions that signify the dopaminergic neuronal damage in substantia nigra. MPTP elevated ROS formation differentially in brain regions (cerebral cortex, hippocampus, substantia nigra) with maximal elevation at hippocampus. The changes in thyroid hormone (T₄ and T₃) levels indicate that brain regions might combat the adverse situation by keeping the levels of thyroid hormones either unchanged or in the elevated conditions in the latter phases (day-3 and day-7), apart from the depletion of thyroid hormones in certain brain regions (T₄ in SN and hippocampus, T₃ in hippocampus) as the immediate (day-1) effects after MPTP treatment. MPTP caused alterations of cellular morphology, RNA:Protein ratio and TPO protein expression, concomitantly depleted TPO mRNA expression and elevated TSH levels in the thyroid gland. Although T₄ levels changed differentially, T₃ levels remained unaltered in thyroid gland throughout the post-treatment days. Results have been discussed mentioning the putative role of T₄ and TSH in apoptosis and/or proliferation/differentiation of thyrocytes. In blood, T₄ levels remained unchanged while the changes in T₃ and TSH levels did not signify the clinical feature of hypo/hyperthyroidism of animals. In the pituitary, both T₄ and T₃ levels remained elevated where TSH differentially altered (elevated followed by depletion) during post-treatment days. Notably, T₄, T₃ and TSH levels did not alter in hypothalamus except initial (day-1) depletion of the T₄ level. Therefore, the feedback control mechanism of hypothalamo-pituitary-blood-thyroid-axis failed to occur after MPTP treatment. Overall, MPTP altered thyroidal status in the brain and peripheral tissues while both events might occur in isolation as well.

Thyroid hormone level is associated with motor symptoms in de novo Parkinson's disease

Sympathetic denervation has been observed not only in the myocardium but also in the thyroid of patients with Parkinson's disease (PD). We investigated whether sympathetic denervation as indicated by decreased cardiac (123)I-meta-iodobenzylguanidine uptake is associated with the levels of thyroid hormones and whether the levels of thyroid hormones affect clinical manifestations in patients with PD. The subjects were 75 patients with de novo PD and 20 age-matched healthy controls. We examined the levels of thyroid-stimulating hormone, free triiodothyronine, and free thyroxine, and evaluated the associations of these levels with cardiac (123)I-meta-iodobenzylguanidine uptake and motor symptoms. The results showed that the free triiodothyronine level was below the normal range in 29 patients (approximately 40 %) and was significantly lower in the patients with PD than in the controls. The decreased free triiodothyronine level was associated with akinetic-rigid motor subtype and washout ratio of cardiac (123)I-meta-iodobenzylguanidine scintigraphy. The free triiodothyronine level negatively correlated with disease severity. Thyroid-stimulating hormone level was within normal range. However, its level was lower in patients with tremor-dominant type or mixed type than in those with akinetic-rigid type. All correlations of these variables with the levels of thyroid hormones remained statistically significant on multiple regression analysis. Our results suggest that the thyroid hormone level, especially the free triiodothyronine level, is closely related to motor symptoms in patients with de novo PD. Further studies are needed to clarify whether the decreased hormone levels have functional roles in motor and non-motor symptoms.

Parkinson's disease and thyroid dysfunction

BACKGROUND

Although no causal linkage between hypothyroidism and Parkinson's disease (PD) has been demonstrated so far, both share common manifestations and coexistence can be a source of diagnostic delay and confusion.

PURPOSE

To assess thyroid function in patients with PD.

SCOPE

Ninety-five PD patients and 102 age-matched controls were assessed for hypothyroidism through clinical evaluation and laboratory screening.

RESULTS

In the PD group 13.7% were hypothyroid versus 10.8% in the control group. Statistical analysis did not show a significant difference (p = 0.3681).

CONCLUSION

Although hypothyroidism was not more prevalent in our PD patients in comparison with the control group, we believe that given the potential overlap of symptoms and signs, thyroid function should be assessed in patients showing worsening of symptoms that cannot be explained by disease progression or resistance to therapy adjustment; screening should take into account the particular acute effect of levodopa on serum TSH levels.

Hypothyroidism and Parkinson's disease and the issue of diagnostic confusion

Development of hypothyroidism may easily be overlooked when occurring together with Parkinson's disease (PD), because many of the symptoms of the two disorders are similar. We report on a case of a woman suffering from both PD and hypothyroidism and review the literature on the subject.

Prevalence, etiology, and treatment of depression in Parkinson's disease

Parkinson's disease (PD) is primarily a disease of elderly individuals with a peak age at onset of 55 to 66 years. It is characterized by bradykinesia, rigidity, tremor, and postural instability; and affects approximately 1 million individuals in the US and is the second most common neurodegenerative disease next to Alzheimer's disease. The motor symptoms of PD are the focus of pharmacotherapy, yet the nonmotor symptoms (e.g., dementia, psychosis, anxiety, insomnia, autonomic dysfunction, and mood disturbances) can be the most disturbing, disabling, and misunderstood aspects of the disease. Depressive symptoms occur in approximately half of PD patients and are a significant cause of functional impairment for PD patients. There is accumulating evidence suggesting that depression in PD is secondary to the underlying neuroanatomical degeneration, rather than simply a reaction to the psychosocial stress and disability. The incidence of depression is correlated with changes in central serotonergic function and neurodegeneration of specific cortical and subcortical pathways. Understanding comorbid depression in PD may therefore add to the understanding of the neuroanatomical basis of melancholia.

Parkinsonism associated with Addison's disease

We describe a 35-year-old woman who developed parkinsonism in association with Addison's disease. The parkinsonism disappeared following treatment for Addison's disease without the use of antiparkinsonian drugs. This association stands unique although the pathophysiology remains unclear.

Subclinical thyroid disease in patients with Parkinson's disease

The objective of this study was to determine whether hypothyroidism is more common in Parkinson patients than in a control group without Parkinson, as suggested in the past. We performed a retrospective file review of all admissions to the geriatric ward during a 1-year period. Concentrations of thyroid stimulating hormone (TSH) and thyroxine (T4) from 92 Parkinson patients were compared with those of 225 randomly selected controls from the same ward. Hypothyroidism was not found to be more common in patients with Parkinson disease as previously suggested. Incidentally, we found an unexpected increase in the prevalence of abnormal thyroid laboratory tests in this group. Statistically significant differences were found in two subgroups, (1) men with Parkinson were more likely to have abnormal thyroid laboratory tests as compared with controls; and (2) 'subclinical' hyperthyroidism was found to be more prevalent in Parkinson patients than in controls. Further research in this field is warranted in non-hospitalized patients.