FRI396 Coexisting Secondary Selective Adrenal Insufficiency And Primary Hypothyroidism In A Patient Previously Treated With Pembrolizumab As Breast Cancer Therapy

Disclosure: R.A. Mayers: None. Background: The novel use of checkpoint inhibitors has increased the development of Immune-related endocrinopathies, being the thyroid and the adrenal axis among the most commonly affected, although co-existence of both pathologies is not commonly reported. Clinical case: A 77-year-old woman was seen in the office for management of her multiple endocrinopathies after receiving Pembrolizumab therapy for triple negative receptor breast cancer. Ten months ago, she was started on a weekly based therapy with Pembrolizumab. Thyroid function tests were monitored on a monthly basis and initially resulted as normal. Five months after initiation of her therapy, she started to complain of nausea, dizziness and confusion. At that time, she was taken to the emergency department by her husband and was found to be hypotensive and with signs of dehydration. Her initial laboratory work was remarkable for adrenocorticotropic hormone levels lower than 5 pg/mL and her total random cortisol level of 4.5 mcg/dl. At that time, she was started on prednisone therapy and later transitioned to hydrocortisone 20mg in the morning and 10 mg at night. During her emergency evaluation her thyroid function tests were unremarkable. Twenty days after her discharge from the hospital her thyroid stimulating hormone level was rechecked and resulted as 37.18 mIU/L . She was started on levothyroxine therapy with 50 mcg daily. Pembrolizumab therapy was stopped after 6 months of initiation. Most recent laboratory work shows persistently elevated levels of thyroid stimulating hormone 11.21 mlU/L, with normal levels of free thyroxine ( 1.4 ng/dl) and total triiodothyronine (125 ng/dl) and negative markers of autoimmunity ( thyroglobulin antibodies level less than 1 IU/ml and thyroid peroxidase antibodies levels of 1 IU/ml). Her adrenal axis remains suppressed with adrenocorticotropic hormone levels less than 5 pg/Ml and morning cortisol level less than 0.05 mcg/dl after a trial off the steroid replacement. Follicle stimulating hormone, luteinizing hormone, insulin grow factor 1 and prolactin levels were checked and were within normal limits. Magnetic resonance of her brain with and without contrast did not show lesions on pituitary gland. Conclusion: This is one of the few cases reported of the co-existence of secondary adrenal insufficiency and primary hypothyroidism after therapy with Pembrolizumab. Presentation: Friday, June 16, 2023