Discussion: The pituitary gland is the master gland of the body because it controls most of the body's endocrine functions by means of the hypothalamic-pituitary axis. The anterior lobe of the pituitary gland secretes 6 hormones: thyroid-stimulating hormone (TSH), previously adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), leuteinizing hormone (LH), growth hormone (GH), and prolactin (PRL). The posterior pituitary gland secretes vasopressin and oxytocin.
Findings: In children, the height of normal pituitary gland can be evaluated as a function of age. Pituitary gland heights (PGHs) have been measured on strictly sagittal T1-weighted images obtained with 3- to 7-mm-thick sections. The measurement is taken at the greatest height, which is usually the midpoint. PGH physiologically enlarges at birth, at puberty (6-7 mm), during pregnancy (<10 mm), and after birth (<12 mm). Sex-related differences in the PGH are observed. In the age group of 10-69 years, pituitary height is greater in female individuals then in male individuals. The pediatric patients aged 0-9 years, both sexes have minimal pituitary height. Maximal height is observed in the 10- to 19-year age group. The height gradually decreases with age after 20 years. In a study by Suzuki et al (1990), no female subjects had a PGH of 9 mm or more, and not male subjects had a PGH of 8 mm of more.
Nonneoplastic cysts are seen in 20% of autopsies and may represent a normal variant or glandular degeneration. In women of childbearing age, the pituitary gland varies substantially in size over the course of the menstrual cycle. In these women, the normal gland may have a convex superior surface, and it may appear to bulge out of the sella turcica.
On MRI, the normal anterior pituitary gland and its stalk return uniform isointensity relative to gray matter. These structures also show intense enhancement after the administration of contrast agent. The gland may be hyperintense in neonates and in pregnant women. The normal posterior pituitary appears bright on T1-weighted MRIs. In about 10% of individuals, MRIs show focal pituitary abnormalities, which are thought to represent protein molecules in the gland.
On dynamic contrast-enhanced imaging, enhancement occurs in an expected sequence because of the unique and separate blood supplies to the pars nervosa, infundibulum, and pars distalis by the inferior hypophyseal artery, superior hypophyseal artery, and the portal system, respectively. The earliest enhancement of normal structures is seen in the infundibulum and in the posterior lobe of the pituitary gland, followed by gradual enhancement of the anterior lobe from the junction of the infundibulum to the peripheral portion of the anterior lobe of the pituitary gland. Peak enhancement of pituitary adenomas usually occurs after the marked enhancement of the normal pituitary gland appears. By virtue of the differential enhancement pattern, adenomas are best seen in the early phase of gadolinium-enhanced dynamic imaging; they appear as hypointense lesions against the hyperintense background of the normally enhancing pituitary gland.
In macroadenomas, the aims of imaging are to precisely demarcate the boundary of normal tissue against the tumoral tissue, to assess for invasion of the cavernous sinus, and to demonstrate any mass effect on neighboring structures (eg, optic chiasm). Also critical is the relationship of the lesion to the nearby vasculature. These factors are important from the surgeon's perspective. Invasion of the cavernous sinus is related to biologically aggressive neoplasms and increases the risk of morbidity and mortality with surgical procedures even though the tumor remains histologically benign in most cases.
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11-YEAR-OLD MALE WITH HISTORY OF HYPOGONADISM
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