Can Lyme disease mess with your thyroid?

Only a handful of studies have described an association between Lyme disease and thyroid dysfunction, while even fewer have shown Lyme disease to cause both thyroiditis and carditis.

In their article “Coexisting Thyroiditis and Carditis in a Patient with Lyme Disease: Looking for a Unifying Diagnosis,” Zarghamravanbakhsh and colleagues described the case of a 53-year-old woman who was found to have carditis and painless, autoimmune thyroiditis, likely due to Lyme disease.¹

A few days after returning from a trip to Delaware, the woman developed headaches, heat intolerance, near-syncope (a feeling that you may faint), and a 5 x5 centimeter rash on her chest.  Although she did not recall having a tick bite, she had several encounters with deer during her visit to Delaware.

One week later, her symptoms progressed. She reported having shortness of breath on exertion and palpitations.

Initially, the woman was diagnosed with Lyme carditis, after her ECG (electrocardiogram) showed a first-degree AV block.

Lyme disease and thyroid tests are positive

The woman also presented with abnormal thyroid tests with a high free thyroxine (T4) and low TSH. Her TSH had been normal four months earlier. Thyroid peroxidase antibodies were present but the thyroid-stimulating immunoglobulin was not.

“Her iodine-123 thyroid scan and 24-hour uptake showed a decrease in iodine uptake of 1.2%, consistent with thyroiditis,” wrote the authors.

She was treated with IV ceftriaxone 2 gm/day for presumed Lyme carditis, along with a 3-week course of doxycycline following her hospital stay.

“Autoimmune thyroiditis can be caused by Lyme disease.”

Testing for Lyme disease by Western blot was positive.

Her low TSH and high free thyroxine (T4) normalized after antibiotic treatment for Lyme disease.

“This case report demonstrates the importance of considering Lyme disease as a unifying diagnosis in patients with concurrent carditis and thyroiditis,” the authors wrote.

The authors discussed previous cases where Lyme disease affected the thyroid:

• “Paparone described a case in which Lyme disease was superimposed on primary hypothyroidism.”
• “Dhliwayo et al., reported a case of a 22-year-old woman with Lyme disease whose thyroid function tests were consistent with transient thyrotoxicosis and decreased radioiodine uptake in the thyroid.”
• “Deol et al described the association of Lyme disease with thyroiditis.”

“In our patient, known exposure to the vector, a classic rash on the chest, improvement in the symptoms, and normalization of thyroid function tests after antibiotic therapy support Lyme infection as a cause of carditis and painless, autoimmune thyroiditis.”

The authors cautioned that thyroid disease can produce false-positive Lyme serology and conduction derangements in the heart.