Effects on the Hypothalamo-Pituitary Axis in Patients with CNS or Head and Neck Tumors following Radiotherapy

SIMPLE SUMMARY: The effects of radiation on the hypothalamic-pituitary axis have been discussed for several decades, but many unknowns remain. Among them, the hypothalamic and/or pituitary dose at risk of causing a deficit, the rate and time of onset of the latter and the possible superiority of one irradiation technique over another. This information will allow a more appropriate follow-up of each patient and early management of radiation-induced toxicities. Reported neuroendocrine impairment after radiotherapy is very heterogeneous. We found new deficiencies occurred in 40% of patients within a median follow-up of 5.6 years. We found differences in sensitivity between the anterior pituitary axes, with the growth hormone axis being the most easily damaged by irradiation and the thyroid hormone axis the least sensitive. Pituitary gland protection and early detection of deficiencies need further investigations. ABSTRACT: Background: Knowledge about the precise effects of radiotherapy on hypothalamo-pituitary functions is limited. Reduction of side effects is a major goal of advanced radiotherapy modalities. We assessed strategies for monitoring and replacement of hormone deficiencies in irradiated patients. Methods: A search strategy was systematically conducted on PubMed(®). Additional articles were retrieved to describe endocrine mechanisms. Results: 45 studies were evaluated from 2000 to 2022. They were predominantly retrospective and highly heterogeneous concerning patient numbers, tumor types, radiotherapy technique and follow-up. Endocrine deficiencies occurred in about 40% of patients within a median follow-up of 5.6 years without a clear difference between radiotherapy modalities. Somatotropic and thyrotropic axes were, respectively, the most and least radiosensitive. Conclusions: Current pituitary gland dose constraints may underestimate radiation-induced endocrine deficiencies, thus impairing quality of life. Little difference might be expected between radiation techniques for PG tumors. For non-PG tumors, dose constraints should be applied more systematically.