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A prolactin cell (also known as a lactotropic cell, epsilon acidophil, lactotrope, lactotroph, mammatroph, mammotroph) is a cell in the anterior pituitary which produces prolactin (a peptide hormone) in response to hormonal signals including dopamine (which is inhibitory), thyrotropin-releasing hormone and estrogen (especially during pregnancy), which are stimulatory.
Prolactin has a wide variety of effects. It stimulates the mammary glands to produce milk (): increased serum concentrations of prolactin during pregnancy cause enlargement of the mammary glands and prepare for milk production, which normally starts when levels of progesterone fall by the end of pregnancy and a suckling stimulus is present.
During pregnancy, the production of prolactin by the mother increases steadily, starting at 6–8 weeks of gestation and continuing until the end of the pregnancy. [32] Prolactin levels in the human fetal circulation see a gradual increase from around 30 weeks of gestation until birth. [ 32 ]
High levels of prolactin during pregnancy and breastfeeding also increase insulin resistance, increase growth factor levels (IGF-1) and modify lipid metabolism in preparation for breastfeeding. During lactation, prolactin is the main factor maintaining tight junctions of the ductal epithelium and regulating milk production through osmotic balance.
The step lengthens as the pregnancy progresses, due to weight gain and changes in posture. On average, a woman's foot can grow by a half size or more during pregnancy. In addition, the increased body weight of pregnancy, fluid retention, and weight gain lowers the arches of the foot, further adding to the foot's length and width.
In addition to their role in lobuloalveolar growth, prolactin and hPL act to increase the size of the nipple-areolar complex during pregnancy. [42] By the end of the fourth month of pregnancy, at which time lobuloalveolar maturation is complete, the breasts are fully prepared for lactation and breastfeeding. [30]
The mechanism is not well understood, but prolactin and its receptors are known to be involved in pseudopregnancy. [3] The role of prolactin in maintaining pseudopregnancy is evident. For instance in the rodent, if chronic prolactin is administered the pseudopregnancy will continue, whereas the condition only lasts a few days if not ...
However, the relative affinities of hPL and prolactin for the human prolactin receptor have yet to be published and the effects of hPL on normal human mammary epithelial tissue have not yet been investigated, and so a definitive role of hPL in human mammary gland development during pregnancy has not been established at present. [6]