The use of neuroimaging for assessing disorders of pituitary development

Abstract

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.

Magnetic resonance imaging of CNS in 15 043 children with GH deficiency in KIGS (Pfizer International Growth Database)

“…The MRI findings included i) normal or hypoplastic pituitary gland without anatomical abnormalities of the hypothalamus or pituitary stalk and ii) moderateto-severe (vertical height %3 mm) hypoplastic pituitary gland with ectopic posterior pituitary located anywhere from the median eminence to the distal stalk (25).…”

“…The frequency of these radiological findings and their endocrine spectrum is variable. In particular, MPHD is more frequently associated with ectopic posterior pituitary and anterior pituitary hypoplasia than isolated GHD (2,3,5,13,14,15,17,18,20,21,22,23,24,25). The variability between different studies can be ascribed to the degree of restriction in the studies' diagnostic criteria, to the diagnostic limits of GHD itself (transitory deficits, recovery, false positives, etc.)…”

“…and/or to the lack of a convincing standard for a normal size of the pituitary gland among the pre-pubertal paediatric population. Idiopathic MPHD, except for a few genetic conditions of hypopituitarism (25), has been reported less frequently in association with anterior pituitary hypoplasia and normal posterior pituitary and pituitary stalk.…”

“…An ES occurs in 10% of idiopathic GHD (IGHD) (12). MPHD may be associated with a variety of cerebral malformations such as Arnold-Chiari I and II, agenesis of the septum pellucidum, septo-optic dysplasia, vermis dysplasia, syringomyelia, absence of the internal carotid artery, dysgenesis of the corpus callosum, arachnoid cysts and tentorium anomalies with basilar impression (11,20,22,25). The frequency of these radiological findings and their endocrine spectrum is variable.…”

“…In fact, the neuroimaging findings in GHD mainly include the following: first, normal or hypoplastic pituitary gland/empty sella (ES) without anatomical abnormalities of the hypothalamus or pituitary stalk and secondly, moderate-to-severe (pituitary height %3 mm) hypoplastic pituitary gland with ectopic posterior pituitary located anywhere from the median eminence to the distal stalk (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25). Isolated GHD is more commonly observed in the first category while multiple pituitary hormone deficiencies (MPHD) occur more frequently in the second.…”