How soon after radiation therapy should pituitary insufficiency be expected?
Any radiation fields that include the hypothalamic–pituitary area can cause neuroendocrine dysfunction. Irradiation for sellar and parasellar tumors, primary brain tumors, nasopharyngeal carcinoma, acute lymphoid leukemia, and tumors of the skull base have been shown to compromise hypothalamic/pituitary function. Depending on the radiation dose and the presence of preexisting pituitary disease, it may take from several months to many years for pituitary insufficiency to develop. The 5-year cumulative incidence of GH deficiency, gonadotropin deficiency, ACTH deficiency, and TSH deficiency in patients with pituitary tumors (radiation dose: 30–50 Gy) and those with nasopharyngeal carcinoma (radiation dose: > 60 Gy) were 100%, 57%, 61%, and 27%, respectively, and 63%, 31%, 27%, and 15%, respectively. Regular testing is mandatory to ensure timely diagnosis and early treatment.