Hypophysitis secondary to pembrolizumab: a case report and review of the literature.

Pembrolizumab is a mAb against the programmed cell death protein-1 (PD-1). It has been approved for the treatment of advanced melanoma (unresectable or metastatic) in adults. Side effects associated with the use of anti-PD-1 are usually considered well tolerated; nevertheless, there are immune-related adverse events that may require treatment discontinuation. A 79-year-old man diagnosed with stage IV right scapular melanoma experienced unspecific symptoms and alterations of the hypothalamus-hypophysis axis after six cycles with pembrolizumab. The case was compatible with immune-related hypophysitis. Autoimmune thyroiditis and primary hypophysitis were excluded and toxicity due to pembrolizumab was considered the cause of hypophysitis. Pembrolizumab was discontinued and toxicity was managed with corticosteroids and hormonal replacement therapy (HRT). After 7 months of follow-up, symptoms were controlled with HRT but thyrotropin and corticotropin hormones had not recovered. It was decided not to reintroduce immunotherapy. Although endocrine disorders are common with the use of anti-PD-1, hypophysitis is very rare. However, clinical signs and symptoms can be nonspecific, therefore, it has probably been underdiagnosed. Monitoring hormones before and during the treatment is important for an early diagnosis and also to replace the alterations with HRT to control the symptoms. Hormonal function does not always recover, but it does not mean immunotherapy cannot be restarted and it should be evaluated in every case.