Iatrogenic Pituitary Shutdown: A Rare Adverse Event of Programmed Cell Death-Ligand 1 Inhibitor

Area of Science:

• Endocrinology
• Oncology
• Immunology

Background:

• Immune checkpoint inhibitors (ICIs) represent a significant advancement in cancer therapy.
• Immune-related adverse events (irAEs) are known complications of ICI treatment.
• Adrenal insufficiency is a rare irAE, more commonly associated with CTLA-4 inhibitors than PD-L1 inhibitors.

Observation:

• A 74-year-old male patient with hepatocellular carcinoma developed symptoms of central adrenal insufficiency after 33 weeks of atezolizumab (a PD-L1 inhibitor).
• Brain imaging revealed no apparent cause for the adrenal insufficiency.
• The patient had pre-existing incidentally discovered central hypothyroidism (low TSH and thyroxine) for which he had initiated replacement therapy.

Findings:

• This case highlights a rare instance of central adrenal insufficiency potentially linked to PD-L1 inhibitor therapy.
• The co-occurrence with central hypothyroidism warrants careful evaluation of pituitary function in patients receiving ICIs.

Implications:

• Clinicians should maintain a high index of suspicion for adrenal insufficiency in patients treated with ICIs, even those on PD-L1 inhibitors.
• Regular monitoring of pituitary hormones is recommended for patients on ICIs.
• It is essential to investigate pituitary hormonal deficiencies, including central hypothyroidism, before initiating hormone replacement therapy.