Research Blog

May 6, 2024

Thyroid Dysfunction and Movement Disorders

There is overlap between movement disorders and neuroendocrine abnormalities.

The relationship between movement disorders and thyroid dysfunction is well-established, with both hypo- and hyperkinetic movement disorders potentially arising from thyroid abnormalities.

These disorders and their symptoms are often interlinked through shared pathogenic pathways, such as hormonal imbalances and inflammatory processes.

Clinical improvement in movement disorder symptoms is frequently observed once thyroid hormone levels are normalized.

Therefore, it's recommended that thyroid function be routinely assessed and managed in patients who present with new, resistant, or worsening movement disorders, ensuring that any thyroid-related issues are addressed to optimize treatment outcomes.

Certain medications for movement disorders, including dopamine and its derivatives, can disrupt thyroid metabolism by affecting TSH (thyroid-stimulating hormone) levels. These drugs, particularly dopamine agonists like bromocriptine, suppress the hypothalamic-pituitary-thyroid axis and inhibit TSH secretion through the activation of dopamine D2 receptors.

Hypothyroidism

Hypothyroidism can be associated with both hypokinetic and hyperkinetic movement disorders.
The relationship between hypothyroidism and movement disorders may be causal, coincidental, or result from one condition unmasking the other.
Hypothyroidism-related parkinsonism often mimics idiopathic Parkinson's disease in its presentation.
Hyperkinetic disorders associated with hypothyroidism typically arise in the context of Hashimoto's disease, featuring symptoms like tremor, myoclonus, and ataxia.
Congenital hypothyroidism resulting in movement disorders such as chorea and dystonia due to genetic diseases is rare.

Hyperthyroidism

Hyperthyroidism commonly leads to hyperkinetic movement disorders, with tremor occurring in about 75% of patients.
Other movement disorders associated with hyperthyroidism include chorea, dystonia, myoclonus, ataxia, paroxysmal movement disorders, and parkinsonism.
There is a noted correlation between the intensity of movement disorders and thyroid hormone levels in hyperthyroid patients.

Common thyroid disorders and clinical manifestations

Pathology	Thyroid function
Iodine deficiency	Hypothyroidism (euthyroidism)
Hashimoto thyroiditis	Hypothyroidism (rarely with euthyroidism)
Autonomous thyroid, Graves' disease	Hyperthyroidism (rarely with euthyroidism)
Subacute thyroiditis (de Quervain)	(Self‐limited) hyperthyroidism, (euthyroidism, hypothyroidism)
Malignancy	Euthyroidism
Cyst	Euthyroidism
Drug‐induced (see Table S1)	Euthyroidism, hypothyroidism, hyperthyroidism

Interpretation of basic thyroid function tests

TSH	Free T4	Interpretation
Normal	Normal	Euthyroidism
High	Low	Primary hypothyroidism
High	Normal	Subclinical hypothyroidism
Low	High	Primary hyperthyroidism
Low	Normal	Subclinical hyperthyroidism

Main antibodies associated with thyroid disease and their overlap

TPOAb, Anti‐thyroid peroxidase antibody; TGAb, Thyroglobulin antibodies, TSAb, THS receptor simulating antibody; TBAb, TSH receptor blocking antibody.

Thyroid dysfunction arises from various causes and is diagnosed using clinical evaluations, biochemical assessments such as TSH, FT4, and FT3 levels, thyroid antibodies, and imaging like thyroid ultrasound. Additional diagnostic methods like scintigraphy or functional thyroid tests may be used for specific cases.

Elevated TSH levels generally indicate hypothyroidism, whereas low TSH levels suggest hyperthyroidism, with increased antibody levels pointing to autoimmune or inflammatory thyroid diseases.

Optimal Takeaways

There is a recognized link between thyroid dysfunction and various movement disorders, which can manifest as either hypo- or hyperkinetic symptoms.
Shared pathogenic pathways like hormonal imbalances and inflammation often underlie both thyroid issues and movement disorders.
Normalizing thyroid hormone levels typically improves symptoms of movement disorders, whether they are idiopathic or have a genetic basis.
It is advisable to evaluate and correct thyroid function in patients presenting with new, unresponsive, or worsening movement disorders to ensure effective management.

Reference

Schneider, Susanne A et al. “Thyroid Disorders and Movement Disorders-A Systematic Review.” Movement disorders clinical practice vol. 10,3 360-368. 3 Feb. 2023, doi:10.1002/mdc3.13656 This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc-nd/4.0/ License