ODP290 A Rare Case of Hypopituitarism Secondary to Radiation Therapy for Nasopharyngeal Carcinoma

Radiation therapy with or without chemotherapy remains a mainstay of treatment for nasopharyngeal carcinomas. Radiation can cause neurological complications such as cranial nerve palsies, and brachial plexopathy as well as non-neurological complications including endocrinopathies like primary hypothyroidism and hypopituitarism. We describe a 30-year-old male with a diagnosis of nasopharyngeal carcinoma who presented to our clinic in June 2021 with low energy level, occasional headache,light-headedness, and poor balance. He received chemo and radiation treatment in 2014 that led to the diagnosis of pituitary hormone deficiency. He also reported erectile dysfunction and decreased libido. His history is remarkable formononucleosis, asthma, and bone fracture in high school while playing football. He developed subsequent hypothyroidism in 2016 and taking Levothyroxine 100 mcg daily since 2016. The patientwas diagnosed with hypogonadism in 2018 and receiving testosterone cypionate injection every 3 weeks. Patient diagnosis of hypothyroidism and hypogonadism prompted to initiate a hypopituitarism workup which lead us to find growth hormone deficiency. Laboratory workup showed low Total Testosterone 43.1 ng/dl (normal range(NR): 264-916), FSH <0.3 IU/L (NR: 1.5-12.4), low IGF-1 56 ng/dl(NR: 83-246), LH <0.3 IU/L(NR: 1.7-8.6),TSH 0.23 uIU/ml(NR: 0.27-4.2), Prolactin Undiluted 55.6,Diluted 49.8 ng/ml(NR: 4.1-18.4), SHBG 86. 0 nmol/L(NR: 16.5-55.9), Normal Free T4 1.4 ng/dl(NR: 0.9-1.8), Free T3 2. 07 pg/ml(NR: 1.8-4.6). Thyroid Antibodies were negative. ACTH-ESO 10 pg/ml(NR: 6-48) and normal Cortisol PM were 4. 0 Ug/dl (NR: 2.7-10.5). We found that he has growth hormone deficiency. We are currently implementing growth hormone supplementation treatment. The patient has been restarted on testosterone injections. Repeated TFTs showed Free T4 0.6 ng/dl, Free T3 1.78 pg/ml and TSH 2.30 uIU/ml. Levothyroxine was increased to 125 mcg daily. This case showed the importance of considering endocrinopathies as late complications of radiation therapy fornasopharyngeal carcinomas. In a cohort study by Tuan et al, primary hypothyroidism and hypopituitarism was reported(Incident rate of 13% and 6% accordingly). Previous studies showed somatotropic axis is the most vulnerable to radiation damage and after radiation, patients developed growth hormone deficiency, adrenal insufficiency, hypogonadism, and thyroid disorders. This case is unique considering that the patient was initially diagnosed with hypothyroidism subsequently hypogonadism and growth hormone deficiency diagnosed years later. Radiation can affect pituitary function. Hypopituitarism can be a late complication of radiation therapy in patients with nasopharyngeal carcinoma. Complete pituitary workup are advised to ensure timely diagnosis and early hormone replacement therapy in these patients. Our case will be helpful to other clinicians for diagnosis and management of endocrinopathies secondary to radiation therapy. Presentation: No date and time listed