[Thyroid dysfunctions secondary to cancer immunotherapy]

The immune checkpoint inhibitors (CPI) such as anti-PD(L)1 or anti-CTLA4 had improved long-term patients' outcomes in different malignancies. Thyroid disorders are the most frequent endocrine side effects from CPI reported in clinical trials and in clinical routine practice. The incidence of thyroid dysfunction is variable according to ICP used (more frequent under anti-programmed cell death 1 (PD1) or anti-programmed cell death-ligand 1 (PDL1)). Most thyroid dysfunctions have been reported to occur 2 to 4 courses after CPI initiation. The clinical symptoms are generally nonspecific (asthenia, weight change, rarely cardiac rhythm disorder). These thyroid dysfunctions are commonly painless thyroiditis with a biphasic evolution: thyrotoxicosis followed by a secondary hypothyroidism frequently definitive. Diagnosis is made on a thyroid test (TSH and FT4). In most cases, no further exam is necessary. Beta blockers therapy is recommended in symptomatic thyrotoxicosis with palpitations. Thyroid hormones therapy will be introduced quickly in case of hypothyroidism. Thyroid dysfunctions are not a contra-indication to the continuation of immunotherapy. Due to the high frequency of these complications, close monitoring of the thyroid status is recommended under CPI.