What is the relationship between Dermatomyositis, Nephrotic Syndrome, and Thyroid (thyroid gland) function?

From the Guidelines

Dermatomyositis patients with nephrotic syndrome should undergo regular thyroid function testing as both conditions can impact thyroid health, and monitoring should be guided by the most recent evidence, such as the 2021 study by 1, which highlights the importance of early detection and management of myositis and its potential impact on thyroid function. The relationship between dermatomyositis, nephrotic syndrome, and thyroid function is complex and multifaceted. Dermatomyositis is an autoimmune disorder that can affect various organs, including the skin and muscles, while nephrotic syndrome is a condition characterized by excessive loss of protein in the urine, often due to kidney damage. Thyroid dysfunction is common in autoimmune disorders like dermatomyositis, and nephrotic syndrome can cause urinary loss of thyroid hormones and binding proteins.

Key Considerations

• Thyroid dysfunction can impact the clinical presentation and management of dermatomyositis and nephrotic syndrome.
• Regular monitoring of thyroid function is essential to prevent complications like cardiovascular issues or worsening muscle weakness.
• The 2021 study by 1 provides valuable insights into the management of myositis, which can inform the approach to monitoring and managing thyroid function in patients with dermatomyositis and nephrotic syndrome.

Recommendations

• Baseline thyroid function tests (TSH, free T4, free T3) should be performed at diagnosis, and monitoring should be done every 3-6 months, especially during disease flares or medication changes.
• If hypothyroidism develops, levothyroxine treatment typically starts at 1.6 mcg/kg/day, adjusted based on TSH levels every 6-8 weeks until stable.
• For hyperthyroidism, beta-blockers (propranolol 10-40 mg three times daily) may provide symptomatic relief while specific treatment is determined.
• Corticosteroids used for dermatomyositis can affect thyroid function test interpretation, and medications like amiodarone and lithium can cause thyroid dysfunction.

Clinical Implications

• The interconnection between dermatomyositis, nephrotic syndrome, and thyroid function stems from shared autoimmune mechanisms, altered protein metabolism in nephrotic syndrome affecting thyroid hormone transport, and medication effects on the hypothalamic-pituitary-thyroid axis.
• Regular monitoring allows for early intervention to prevent complications like cardiovascular issues or worsening muscle weakness, as highlighted by the 2021 study by 1.
• A comprehensive approach to managing patients with dermatomyositis and nephrotic syndrome should include regular thyroid function testing and monitoring, guided by the most recent evidence.

From the Research

Relationship Between Dermatomyositis, Nephrotic Syndrome, and Thyroid Function

• Dermatomyositis (DM) has been linked to autoimmune thyroiditis (AIT) in several studies 2, 3.
• A study found that 90.9% of patients with coexistent DM and AIT had hypothyroidism, suggesting a strong relationship between the two conditions 2.
• Another study reported a case of Hashimoto's thyroiditis with clinical manifestations resembling dermatomyositis, highlighting the potential for misdiagnosis 3.
• Nephrotic syndrome (NS) has been associated with thyroid dysfunction, with studies showing that patients with NS are more likely to have abnormal thyroid function tests 4, 5.
• A study found that patients with NS and thyroid dysfunction had higher levels of urine protein, creatinine, and lipid levels, and lower levels of albumin and hemoglobin compared to those with normal thyroid function 4.
• Dermatomyositis has also been linked to nephrotic syndrome, with a case report describing a patient with DM and NS who developed diffuse proliferative glomerulonephritis 6.
• The development of nephrotic syndrome can increase the need for levothyroxine replacement in patients with hypothyroidism, with one study finding that patients required a 17.6% increase in replacement dose 5.

Clinical Implications

• Patients with DM should be routinely evaluated for thyroid function and the emergence of comorbidities, including nephrotic syndrome 2.
• The treatment of corticosteroids combined with levothyroxine may be useful for patients with coexistent DM and AIT 2.
• Clinicians should be aware of the potential for misdiagnosis between DM and Hashimoto's thyroiditis, and consider thyroid function tests in patients with DM-like symptoms 3.
• Patients with NS should be monitored for thyroid dysfunction, and those with hypothyroidism may require adjusted levothyroxine replacement doses 4, 5.