The Pituitary Gland in Pregnancy and the Puerperium

Publisher Summary During pregnancy, the anterior pituitary enlarges greatly; pituitary weight increases by about 33%, as does cross-sectional area and gland. This enlargement results in an upward convexity of the superior surface of the gland when visualized radiologically. In response to a changing hormonal milieu, the human pituitary gland undergoes a remarkable transformation during pregnancy. Substances produced by the fetoplacental unit greatly modify maternal hypophyseal structure and function. In the case of some hormones, for example prolactin (PRL) or oxytocin, such changes clearly play an important functional role in pregnancy, labour, and the puerperium. In the case of others, such as growth hormone (GH), the changes in the maternal pituitary seem to be a coincidental side effect of processes involved in stimulating fetal growth. Other changes noted during pregnancy in immunohistochemical studies include a modest diminution in the relative number of somatotrophs, a major decrease in the proportion of stainable gonadotrophs, and no change in the proportions of thyrotrophs or corticotrophs. Some of the somatotrophs may convert to mammosomatotrophs or lactotrophs during pregnancy.