Central diabetes insipidus (CDI) is the end result of a number of conditions that affect the hypothalamic-neurohypophyseal system. The known causes include germinoma/craniopharyngioma, Langerhans cell histiocytosis (LCH), local inflammatory, autoimmune or vascular diseases, trauma resulting from surgery or an accident, sarcoidosis, metastases and midline cerebral and cranial malformations. In rare cases, the underlying cause can be genetic defects in vasopressin synthesis that are inherited as autosomal dominant, autosomal recessive or X-linked recessive traits. The diagnosis of the underlying condition is challenging and raises several concerns for patients and parents as it requires long-term follow-up. Proper etiological diagnosis can be achieved via a series of steps that start with clinical observations and then progress to more sophisticated tools. Specifically, MRI identification of pituitary hyperintensity in the posterior part of the sella, now considered a clear marker of neurohypophyseal functional integrity, together with the careful analysis of pituitary stalk shape and size, have provided the most striking findings contributing to the diagnosis and understanding of some forms of ‘idiopathic’ CDI. MRI STIR (short-inversion-time inversion recovery sequencing) is a promising technology for the early identification of LCH-dependent CDI.

A diagnostic etiology was achieved in 96% of patients with CDI. Risk stratification based on the degree of pituitary stalk thickness is of prognostic value for long-term outcomes including permanent pituitary dysfunction. New guidance is provided for the management of these patients.

SummaryMagnetic resonance imaging (MRI) is the radiological examination method of choice for evaluating hypothalamo-pituitary-related endocrine disease and is considered essential in the assessment of patients with suspected hypothalamo-pituitary pathology. Physicians involved in the care of such patients have, in MRI, a valuable tool that can aid them in determining the pathogenesis of their patients' underlying pituitary conditions. Indeed, the use of MRI has led to an enormous increase in our knowledge of pituitary morphology, improving, in particular, the differential diagnosis of hypopituitarism. Specifically, MRI allows detailed and precise anatomical study of the pituitary gland by differentiating between the anterior and posterior pituitary lobes. MRI recognition of pituitary hyperintensity in the posterior part of the sella, now considered a marker of neurohypophyseal functional integrity, has been the most striking finding in the diagnosis and understanding of certain forms of 'idiopathic' and permanent growth hormone deficiency (GHD). Published data show a number of correlations between pituitary abnormalities as observed on MRI and a patient's endocrine profile. Indeed, several trends have emerged and have been confirmed: (i) a normal MRI or anterior pituitary hypoplasia generally indicates isolated growth hormone deficiency that is mostly transient and resolves upon adult height achievement; (ii) patients with multiple pituitary hormone deficiencies (MPHD) seldom show a normal pituitary gland; and (iii) the classic triad of ectopic posterior pituitary, pituitary stalk hypoplasia/agenesis and anterior pituitary hypoplasia is more frequently reported in MPHD patients and is generally associated with permanent GHD. Pituitary abnormalities have also been reported in patients with hypopituitarism carrying mutations in several genes encoding transcription factors. Establishing endocrine and MRI phenotypes is extremely useful for the selection and management of patients with hypopituitarism, both in terms of possible genetic counselling and in the early diagnosis of evolving anterior pituitary hormone deficiencies. Going forward, neuroimaging techniques are expected to progressively expand and improve our knowledge and understanding of pituitary diseases.

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