Recognising pituitary and thyroid dysfunction after craniospinal radiotherapy: an underrecognised mixed endocrine toxicity.

Summary: Adult medulloblastoma is a rare cerebellar tumour with an incidence of 0.6-1 per million per year in post-pubertal patients. Craniospinal radiotherapy is a key component of treatment. Endocrine organs commonly involved in the radiation field - such as the hypothalamus, pituitary and thyroid gland - are particularly sensitive to radiation-induced damage, often resulting in hormonal deficiencies in a dose-dependent manner. We report the case of a 43-year-old woman who developed both hypopituitarism and primary hypothyroidism following craniospinal radiotherapy for medulloblastoma at the age of 34. She was diagnosed with primary hypothyroidism two years later. Seven years later, hormonal substitution therapy was started for menopausal symptoms, and nine years later, she presented with persisting long-standing fatigue, amenorrhoea, nausea upon waking, vomiting and anorexia. Laboratory testing was suggestive of hypopituitarism. Dynamic testing confirmed severe growth hormone deficiency but a normal cortisol response. Thyroid-releasing hormone stimulation test revealed a blunted and delayed response. Magnetic resonance imaging revealed significantly reduced pituitary height over time. Although radiation-induced endocrine dysfunction is well documented in children, its prevalence in adult populations also reaches 50%, and its clinical significance is increasingly recognised. Despite the common occurrence of hypothalamic-pituitary axis dysfunction and primary hypothyroidism following craniospinal irradiation, their simultaneous presentation provides an important educational example of the complex and multifaceted endocrine effects of radiation exposure. This paper highlights the importance of minimising radiation dose on these endocrine glands, as well as long-term multidisciplinary follow-up and screening after craniospinal radiotherapy. It also raises the question whether pituitary evaluation on surveillance imaging could help predict pituitary dysfunction, a possibility that warrants further exploration. Learning points: Hypopituitarism and primary hypothyroidism are common complications following craniospinal irradiation, but symptoms are often insidious and progressive. Pituitary and thyroid dysfunction post-craniospinal radiotherapy is dose-dependent, underscoring the importance of minimising radiation dose to these endocrine organs. Structured endocrine screening and lifelong multidisciplinary follow-up are valuable for early detection and treatment. Routine brain surveillance imaging with pituitary gland assessment might aid in predicting pituitary dysfunction, but its exact role and correlation need to be elucidated.