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Introduction
  • Source
    • lactotrophs in the anterior pituitary synthesize prolactin
      • during pregnancy there is an increase in lactotrophs
      • it is chemically similar to growth hormone
  • Regulation
    • prolactin secretion is regulated by chemicals that alter prolactin gene transcription
      • stimulatory
        • thyrotropin-related hormone (TRH)
        • pregnancy
        • breastfeeding
          • suckling stimulates afferent fibers to inhibit hypothalamic dopamine secretion
        • dopamine antagonists such as anti-psychotics
        • sleep
        • stress
      • inhibitory
        • dopamine
          • this is a catecholamine that tonically inhibits prolactin secretion in non-pregnant and non-lactating patients
          • dopamine mainly arises from hypothalamic dopaminergic neurons
            • there are also dopaminergic neurons in the posterior lobe of the pituitary
        • dopamine agonists
          • cabergoline
          • bromocriptine
        • prolactin
          • it inhibits its own secretion via upregulating hypothalamic dopamine synthesis and secretion (negative feedback)
        • somatostatin
  • Function
    • milk production (lactogenesis)
      • prolactin stimulates the production of milk components (e.g., lactose and casein)
        • during pregnancy elevated levels of estrogen and progesterone decrease prolactin receptor numbers in the breast
          • this is why lactation does not occur during pregnancy but at parturition
            • recall that at parturition estrogen and progesterone levels decrease
    • breast development
      • stimulates the mammary ducts to proliferate and branch
        • this is accomplished with the help of estrogen and progesterone
    • inhibits ovulation
      • prolactin inhibits gonadotropin-releasing hormone (GnRH) synthesis and secretion
        • this explains why fertility is decreased during breastfeeding
  • Clinical correlate
    • hyperprolactinemia
      • etiology
        • prolactinoma
        • antipsychotics
      • symptoms
        • galactorrhea
        • infertility
      • treatment
        • dopamine agonists such as
          • cabergoline
          • bromocriptine
 
 

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