Adrenal Insufficiency Masquerading as Primary Hypothyroidism Following Immune Checkpoint Inhibitors Treatment

Background: Immune checkpoint inhibitors (ICIs) are novel immunotherapy agents that have been used to treat multiple advanced cancer. Even though they confer potential clinical advantages by regulating immune reactions, they have been linked with serious immune-mediated adverse events. Here we present a case of a patient who was treated with ICIs, Nivolumab (programmed death-1 inhibitor) and Ipilimumab (cytotoxic T lymphocyte antigen-4 inhibitor), and subsequently developed two concurrent immune-related endocrine disorders. Clinical Case: An 83-year-old man with advanced renal cell carcinoma presented with generalized weakness. He had finished four cycles of immunotherapy with Nivolumab and Ipilimumab, and Ipilimumab was discontinued afterward. Two days after the fifth cycle of immunotherapy with Nivolumab, he developed worsening fatigue, nausea, and anorexia. He appeared mildly volume depleted with borderline hypotensive (104/63 mmHg). The rest of the physical exam was unremarkable. Initial tests showed elevated levels of TSH (13.15 uIU/mL, ref 0.45–5.33 uIU/L), reduced levels of free T4 (<0.25 ng/dL, ref 0.58–1.64 ng/dL), free T3 (1.72 pg/mL, ref 2.5–3.9 pg/mL), negative thyroglobulin antibody, and elevated levels of thyroid peroxidase antibody (429 IU/mL, ref <9 IU/mL), thus suggesting primary hypothyroidism. Serum levels of sodium and potassium were unremarkable (136 meQ/L, ref 136–145 mEq/L; 3.6 meQ/L, ref 3.5–5.1 meQ/L respectively). His baseline TSH was normal three months prior to arrival (1.31 uIU/mL) and suppressed one month prior to arrival (0.01 uIU/mL). Immune-related thyroiditis with immune checkpoint inhibitors was suspected. He was given levothyroxine and observed in the hospital. After two days of hospitalization, weakness had slightly improved. However, he still had persistent nausea. He also developed low blood pressure (90/47 mmHg) and mild hyponatremia (133 mEq/L) with a normal potassium level. Further investigation showed low cortisol (1.0 ug/dL, ref 5.0–21.0), low ACTH (13 pg/mL, ref 6–50 pg/mL), cortisol level at 30 and 60 minutes post-cosyntropin stimulation test of 10.8 ug/dL (ref 13.0–30.0 ug/dL) and 14.8 ug/dL (ref 14.0–36.0 ug/dL) respectively, and negative adrenal antibodies, suggesting of secondary adrenal insufficiency due to hypophysitis. The patient was started on hydrocortisone, and his symptoms improved afterward. Conclusion: This case report highlights the common pitfall of managing immune-related endocrine disorders of ICIs. Adrenal insufficiency may present with a broad range of nonspecific symptoms, which could be attributed to hypothyroidism, underlying illness, or medications. Although a rare adverse effect, it is prudent to recognize adrenal insufficiency superimposed on primary hypothyroidism. Introducing thyroxine before replacing glucocorticoids can lead to an adrenal crisis.