Endocrine Abstracts

Introduction: Radiotherapy to the head and neck area is the standard therapy used for the treatment of nasopharyngeal carcinoma. Hypopituitarism is a well-known late complication of cranial radiotherapy. Although very rarely, it may be observed following radiotherapy to the head and neck area, as well.

Case report: A 53-year-old man was referred to our endocrinology department for hyponatremia and low free thyroxine (T₄) with normal thyroid- stimulating hormone levels. His medical history was remarkable only for the nasopharyngeal carcinoma that had been treated with radiation and chemotherapy seven years before admission. He had been hospitalized many times due to hyponatremia in other hospitals within the last six months. He had been discharged every time after the correction of his serum sodium levels.

On physical examination, he was pale and lethargic. Blood pressure was 85/50 mmHg, heart rate was 74 bpm. His random cortisol level was 3 μg/dl. Besides cortisol, his testosterone, luteinizing hormone and insulin-like growth factor-1 levels were also below normal limits. Magnetic resonance imaging (MRI) exhibited normal findings in his pituitary. Based on these results, the patient was diagnosed to have panhypopituitarism due to the radiotherapy that he once had for his nasopharyngeal carcinoma. Hormonal substitution therapy with IV glucocorticoids and levoT₄ was started sequentially. His serum sodium level gradually rose up to normal limits. He no longer required intravenous sodium replacement.

Conclusion: Hyponatremia is often seen in patients with adrenal insufficiency but the diagnosis of hypopituitarism in hyponatremic patients is often overlooked and these patients had been admitted to the hospitals many times before the underlying hypopituitarism was diagnosed. Radiotherapy to the head and neck area may cause hypopituitarism and thus hyponatremia in long term follow-up. Taking careful medical history plays the pivotal role in making the correct diagnostic approaches.