When Hormones are Being Difficult: A Rare Case and the Literature Review of Pembrolizumab-Induced Polyendocrinopathy.

Immune Checkpoint inhibitors (ICIs) such as nivolumab, pembrolizumab, and ipilimumab are monoclonal antibodies against cytotoxic T lymphocyte antigen 4 (CTLA4) or program death (PD)1 and its ligand PDL1. Agents targeting PD1, such as pembrolizumab, have shown widespread efficacy in the past and are also associated with a wide range of immune-related adverse events (irAEs), including endocrine toxicities. A 31-year-old female with a medical history significant for Stage IIb Breast cancer on chemo and immunotherapy (pembrolizumab) presented with nausea, vomiting, and generalized abdominal pain. Laboratory studies showed a blood glucose level of 356 mg/dl, elevated Anion gap 18 meq/L, beta-hydroxybutyrate 46 mg/d, and low C-peptide levels <0.10 ng/ml. The patient was treated for Diabetic Ketoacidosis (DKA). Further testing revealed high Thyroid Stimulating Hormone (TSH) levels along with elevated thyroid peroxidase levels of 38 IU/L. After discharge from the hospital on insulin and levothyroxine therapy, the patient reported increasing fatigue and further testing revealed low cortisol levels <0.5 mcg/dl with elevated ACTH consistent with primary adrenal insufficiency. The patient was started on hydrocortisone therapy with improvement in symptoms. Endocrine toxicities are not uncommon in patients receiving pembrolizumab, but polyendocrinopathy in a relatively rare side effect of pembrolizumab. Only a few cases of pembrolizumab-induced polyendocrinopathy have been reported so far which we have mentioned in this article. While patients are on immunotherapy, close monitoring for clinical signs & symptoms can lead to an early diagnosis, substantially improving morbidity and mortality.