Endocrine Abstracts

Introduction: Immune checkpoint inhibitors (ICPIs) are recent approved drugs used in malignant melanoma, non-small-cell lung cancer and renal cell cancer. They act by activating host T cell against malignant antigens. Immune checkpoint blockade can lead to breaking of immune self-tolerance, thereby inducing autoimmune/autoinflammatory side effects, such as endocrinopathies. It may affect thyroid, adrenal and pituitary. We present two ICPIs induced thyroiditis cases.

Case 1: Sixty-eight-year-old female diagnosed with a conjunctival malignant melanoma at the age of 64. She was first surgery treated and then submitted to radiotherapy. Due to bone, lung and hepatic metastasis she started Ipilimumab 3 mg/kg on 21-day cycle. Eleven days after the third Ipilimumab administration she was asymptomatic but was found to have thyrotoxicosis (TSH 0.04 μUI/ml; FT₄ 1.31 ng/dl). Thyroid peroxidase and thyroglobulin antibodies were elevated and thyroid stimulating immunoglobulin was low. Four months after suspension of Ipilimumab a spontaneous recovery of the thyroid axis was seen.

Case 2: Sixty-two-year-old female diagnosed with a foot malignant melanoma one year before. She was first surgically treated. Due to lung, breast and lymph node metastases she started Nivolumab 3 mg/kg on 15-day cycle. Before starting this drug she had a diffuse thyroid uptake on PET-scan with normal thyroid function. Twelve days after the first administration of Nivolumab she described a painless increase of anterior cervical volume, fatigue and had thyrotoxicosis on the blood test (TSH 0.02 μUI/ml; FT₄ 2.50 ng/dl). One month after she was found to have asymptomatic hypothyroidism (TSH 9.96 μUI/ml; FT₄ 0.49 ng/dl). Thyroid ultrasound showed a thyroiditis pattern. She started levothyroxine therapy and one month after stopping Nivolumab she was still on hypothyroidism.

Conclusions: ICI may induce autoimmune thyroiditis or may worsen a pre-existing one. These patients should be monitored for signs and symptoms of thyroid dysfunction, since it can cause significant morbidity if not promptly recognized and treated.