Endocrine morbidity in adults treated with cerebral irradiation for brain tumours during childhood.

Hypothalamic-pituitary function was assessed in 20 adult subjects who were treated with cerebral irradiation for brain tumours during childhood between 8 and 32 years earlier. Nine patients showed impaired growth hormone (GH) responses to hypoglycaemia, of whom, 7 are below the third centile for standing height. All GH deficient subjects received more than 2950 rads to the hypothalamic-pituitary axis with a maximum dose of approximately 5000 rads being used in one case. Three subjects have an elevated basal serum thyroid stimulating hormone (TSH) level and 2 of these show an exaggerated TSH response to thyrotrophin releasing hormone (TRH) but no patient was clinically or biochemically hypothyroid. The rest of hypothalamic-pituitary function was essentially normal. This study shows that multiple pituitary hormone deficiencies do no develop with time when the radiation dose is below a critical level. Thus it appears that there is a gradation of radiation damage to the hypothalamic-pituitary axis which is dependent primarily on the dose received rather than the time interval after radiotherapy.