Context: Hypothalamic-pituitary (HP) dysfunction is common in children treated with cranial radiotherapy (RT) for brain tumors but there is little known about the risk of HP dysfunction in adults treated with RT for primary non-pituitary brain tumors.

Objective: To study the frequency of HP dysfunction in adults after RT for non-pituitary brain tumors

Method: We studied 56 adult patients who received external beam RT for primary non-pituitary brain tumors at time intervals of 12-150 months after RT. The control group consisted of 20 RT-naïve patients with primary brain tumors. GH and adrenal axes were assessed using the insulin tolerance test or the glucagon stimulation test. Gonadotroph, thyrotroph and lactotroph function were assessed using baseline blood measurements. The biological effective dose (BED) to the HP axis was calculated in the RT patients.

Results: Hypopituitarism was present in 41% of patients. The frequency of GH, ACTH, gonadotropin and TSH deficiencies and hyperprolactinemia was 32%, 21%, 27%, 9% and 32% respectively. Any degree of hypopituitarism and GH deficiency were significantly associated with longer time interval from RT and greater BED. However, gonadotropin deficiency and hyperprolactinemia were only related to BED while ACTH deficiency was only significantly associated with the time interval from RT. One RT-naïve patient was GH deficient.

Conclusion: Adult patients treated with cranial irradiation for primary non-pituitary brain tumors are at high risk of hypopituitarism which is time and dose dependent. Long-term surveillance and periodic evaluation is needed. We recommend that adult late effect clinics, similar to those for children, should be established.