Endocrine Abstracts

The adverse effect of childhood cancer and treatment thereof on growth was firmly established in the mid-1970’s. The impact on growth is multifactorial, however, cranial irradiation was quickly established as one of the most important contributors. Exposure of the hypothalamo-pituitary (HP) region to radiation in childhood cancer survivors is now a well-established risk factor for the development of anterior hypopituitarism. The degree of hypopituitarism can vary between isolated deficiency of one axis to deficiency of all the anterior pituitary hormones. Irradiation of brain tumours accounts for the majority of childhood cancer survivors who receive HP axis exposure, however the HP region can also be exposed in treatment of other childhood cancers including nasopharyngeal carcinomas, acute leukaemias with central involvement and total body irradiation. The degree of hypopituitarism is dependent on a number of factors including radiation dose delivered to the HP region; dose fractionation; time since radiation; and degree of compromise of the axes from the tumour and prior surgery. Development of hypopituitarism most frequently follows a pattern, with GH almost exclusively the first axis affected. Thereafter the evolution of deficiencies is gonadotropin, ACTH and TSH deficiency, however TSH deficiency is now recognised to occur earlier than previously thought when based on a fall in free T4 values within the normative range. Diabetes insipidus is not a direct consequence of irradiation and when present other causes should be considered. Under-recognised and less frequently investigated has been the development of hypopituitarism in adult brain tumour survivors, who appear to have a similar incidence of hypopituitarism to childhood brain tumour survivors. Outwith of hypopituitarism, a number of childhood brain tumours receive craniospinal radiation placing these individuals at additional risk of primary hypothyroidism, benign and malignant thyroid nodules, hyperparathyroidism, low bone mass and possibly diabetes mellitus.