From the Guidelines
Parkinson's disease patients with hypothyroidism should be managed with levothyroxine, starting at 25-50 mcg daily, and their thyroid function should be regularly monitored to prevent exacerbation of Parkinson's symptoms. The treatment of hypothyroidism in Parkinson's disease patients is crucial, as thyroid dysfunction can sometimes mimic or exacerbate Parkinson's symptoms 1. For Parkinson's disease, treatment typically begins with carbidopa-levodopa (Sinemet), starting at 25/100 mg three times daily and gradually increasing as needed. Other medications may include dopamine agonists like pramipexole (Mirapex) or ropinirole (Requip), MAO-B inhibitors such as selegiline or rasagiline, or COMT inhibitors like entacapone.
Key Considerations
- Regular monitoring of thyroid function is essential, with thyroid function tests every 6-12 months, to maintain TSH levels between 0.5-2.5 mIU/L 1.
- Parkinson's medications may interact with levothyroxine, potentially affecting absorption, so these medications should be taken at least 2-4 hours apart.
- Nutritional assessment should be conducted at least on a yearly basis, and vitamin status, particularly vitamin D, should be actively monitored, as low vitamin D levels have been associated with the risk of developing Parkinson's disease 1.
- Supplementation with vitamin D should be considered, as it may slow disease progression, at least in patients with high-risk genotype of the vitamin D receptor 1.
Monitoring and Follow-up
- Regular neurological assessments for Parkinson's disease progression and medication effectiveness are essential.
- Monitoring of body weight is recommended, as weight changes can occur in Parkinson's disease patients, and malnutrition has been associated with disease severity 1.
From the Research
Parkinson's Disease and Hypothyroidism
- Parkinson's disease (PD) is a neurodegenerative disorder that can be associated with thyroid dysfunction, including hypothyroidism 2, 3, 4, 5.
- Studies have shown that hypothyroidism can be present in patients with PD, and that the symptoms of hypothyroidism can be masked by the symptoms of PD 2, 4.
- The prevalence of hypothyroidism in patients with PD has been reported to be around 13.7% in one study, although this was not found to be significantly different from the control group 3.
- The relationship between PD and hypothyroidism is complex, and it is thought that dopamine and thyroid hormones may interact in the regulation of each other's levels 5.
- Hypothyroidism can increase the risk of PD, and thyroid disturbances can share some clinical signs with PD, making diagnosis and treatment challenging 5.
Diagnosis and Treatment
- Diagnosis of PD is based on history and examination, and can be improved with the use of dopamine transporter single-photon emission computed tomography 6.
- Treatment of PD is symptomatic, and focused on improvement in motor and nonmotor signs and symptoms 6.
- Dopamine-based therapies are typically used to treat initial motor symptoms, while nonmotor symptoms require nondopaminergic approaches 6.
- Rehabilitative therapy and exercise can complement pharmacologic treatments, and advanced treatments such as deep brain stimulation can be used in cases of medication-resistant tremor or dyskinesias 6.
Thyroid Function in PD
- Thyroid function should be assessed in patients with PD, particularly in those with worsening symptoms that cannot be explained by disease progression or resistance to therapy adjustment 3, 4.
- The potential overlap of symptoms and signs between PD and hypothyroidism means that thyroid function should be evaluated in patients showing worsening of symptoms 3, 4.
- The use of levodopa can interfere with thyroid function, and thyroid hormone replacement therapy may be necessary in some cases 4, 5.