Resident Physician Abington Jefferson Health Willow Grove, Pennsylvania, United States
Introduction: Hypothyroidism presents as slowing of bodily functions that become more severe as the disease progresses. Common causes of acquired hypothyroidism include autoimmune disorders, iodine deficiency, post-radiation and drug induced. We present a rare case of lenalidomide induced severe hypothyroidism leading to acute psychosis requiring aggressive intravenous thyroxine repletion.
Case Description: Sixty-four-year-old male with a history of follicular Non-Hodgkins Lymphoma, currently on rituximab/lenalidomide who was brought to the Emergency Department (ED) for hallucinations, paranoia and manic symptoms for three days. In the ED, his vitals were stable. Computed Tomography (CT) head was normal. Blood work revealed an elevated TSH at 51.70 uIU/ml (normal 0.30-5.0 uIU/ml), free T3 < 0.1 pg/ml (normal 2.0-4.4 pg/ml) and free T4 <0.1 ng/dL(normal 0.7-1.7 ng/dL). Thyroid peroxidase antibody was 9 IU/ml (normal <34.0 IU/ml). He started on intravenous levothyroxine and responded well in about forty-eight hours. During this time, he got a Magnetic Resonance Imaging (MRI) of his brain that was normal. He continued IV therapy for 4 weeks after which he was switched to oral levothyroxine. His chemotherapy regimen has been changed to bendamustine/rituximab. He continues to be on oral levothyroxine and is currently doing well.
Discussion: Hypothyroidism is described as decreased activity of the thyroid gland resulting in retardation in growth and development of children and adults. Autoimmune disorders such as Hashimoto’s thyroiditis remain the leading cause of hypothyroidism in developed countries in contrast to developing countries where iodine deficiency goiter remains endemic. Several drugs are known to cause hypothyroidism such as amiodarone, lithium, check point inhibitors, thalidomide, interleukin-2 and interferon alpha. Recently, lenalidomide has been found to cause hypothyroidism in around five to ten percent of the patients with severe hypothyroidism being reported in only a handful of patients, as most cases are usually mild. The exact mechanism by which it causes hypothyroidism is unknown, but several mechanisms have been hypothesized including decreased iodine uptake by the thyroid gland, decreased thyroid secretion, formation of auto antibodies against the thyroid gland and shrinkage of the thyroid gland due to ischemia. Since symptoms of hypothyroidism overlap with those of cancer patients on chemotherapy including fatigue and hair loss, the diagnosis can be delayed leading to severe or fatal complications. We suggest regular monitoring of a patient’s thyroid profile during treatment with lenalidomide, perhaps every 2-3 months as has been suggested in the oncology literature.