MRI evaluation of size and shape of normal pituitary gland: Age and sex related changes

Introduction: For complete assessment of pituitary gland, we should be aware of its normal anatomy with the physiological variations in its size and shape in different age groups in both males and females. Measurements of the normal pituitary gland for various age ranges are helpful to diagnose pathologies in pituitary gland. Aim: To study the size, shape and mean normal volume of normal pituitary gland in different age groups of both genders with Magnetic Resonance Imaging (MRI). Materials and Methods: It was a retrospective study in which 500 patients were included (261 males and 239 females, ranging from one year up to 80 years of age) who underwent brain MRI in the Radio-diagnosis department. Patients with pituitary or endocrine abnormalities were excluded from the study. All MRI images were acquired on a Siemens Avanto 1.5T MRI machine. Precise mid sagittal T1WI and coronal T2WI were selected for measurement. Statistical calculations were done by Software Open Epi Version 3 for epidemiological age groups. Relation between mean height and age and relation between volume and age were done by ANOVA test, Chi-square test. A p-value <0.05 was considered as significant. Results: The observation was divided into six groups according to age. Mean height of pituitary gland in female patients of each age group was greater than that of male patients in the same age group. Height of pituitary gland reached a maximum in the 20 to 29 years of age group in both males and females, after which, there was a decline in the pituitary height in the subsequent age groups. The overall mean pituitary height in the age group 1-10 years came out to be 5.3±1.4 mm. In the age group 11-20 years, mean pituitary height was 6.2±1.1 mm. In the age group 21-30 years 6.8±1.9 mm, 31-40 years age group 6.3±1.8 mm, in 41-50 years age group 6.5±1.5 mm and individuals above 50 years of age, mean pituitary height was observed as 7±2.1 mm. In all the age groups and both the sexes, the most common shape was flat which was seen in 46% of people followed by convex in 31% and concave shape in 23% people. The mean pituitary volume in the age group 1-10 years came out to be males 210±0.73 mm³ and in females 200±0.75 mm³. In the age group 11-20 years mean pituitary volume in males was 340±127 mm3 and in female’s 280±123 mm³. In the age group 21-30 years, mean pituitary volume in males was 430±116 mm³ and in females 440±180 mm³. In the age group 31-40 years, mean pituitary volume in males was 380±140 mm³ and in females was 440±111 mm³. In 41-50 age groups mean pituitary volume in males was 400±159 mm³ and in females it was 420±116 mm³. In individuals above 50 years of age the mean pituitary volume was observed in males as 410±168 mm³ and 420±174 mm³ in females. Conclusion: Knowledge of physiological variation in the size and shape of pituitary gland is necessary to compare the abnormal increase in the size. In the cases where there is a borderline abnormality in the size and shape of pituitary gland, it should be further evaluated by dynamic contrast study on MRI. Pituitary size and shape evaluation needs to compare with the normal range of height and volume of the normal pituitary gland in various age groups in both genders in Indian population.