Pituitary gland signal in pre-term infants during the first year of life: an MRI study.

Our purpose was to determine the pituitary gland signal of premature neonates and infants. We retrospectively measured, in a midline sagittal T1-weighted MRI scan, the pituitary signal of 121 premature infants (mean gestational age: 32.8 weeks, mean chronological age: 6.9 months, mean corrected age: 5.2 months). The relative signal intensity of the adenohypophysis and neurohypophysis was measured as (A-V)/V and (P-V)/V, respectively (where A, P, V are the mean signal intensities of the adenohypophysis, neurohypophysis and vermis white matter, respectively). On visual inspection the adenohypophysis was rated relative to the vermis white matter (VWM) and scored as hyperintense (grade 3), isointense (grade 2) and hypointense (grade 1). (A-V)/V and (P-V)/V had a negative correlation with chronological age (r=-0.38, r=-0.35, respectively, P<0.01) and corrected age (r=-0.42, r=-0.40, respectively, P<0.01). The (A-V)/V was different in the three grade groups; significant difference was found between grades 3 and 2 and grades 3 and 1. The adenohypophysis was bright in 93% of babies under 2 months of chronological age. In five babies of mean gestational age 29.1 weeks a hyperintense adenohypophysis was observed at 2.9-3.7 months of chronological age (corrected age 0.37-2 months). We conclude that in pre-term babies the adenohypophysis appears in hypersignal that may persist up to 2 months of corrected age. The adenohypophyseal and neurohypophyseal signals decrease with age.