Updated: 10/25/2018

Prolactin

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Topic
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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Questions (2)
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(M1.EC.14.75) A 43-year-old man with a history of schizophrenia, currently controlled with medication, comes in for an appointment with his internist. He is concerned about abnormal discharge from both nipples over the past 3 months. The fluid is white, and he wonders if it could be milk. On further review of systems, he endorses a diminished sexual drive. The physician suspects that one of the patient's medications may be the culprit for these symptoms. Which of the following medications is NOT likely to be the cause? Tested Concept

QID: 106828
1

Metoclopramide

0%

(0/33)

2

Haloperidol

6%

(2/33)

3

Bromocriptine

82%

(27/33)

4

Fluphenazine

3%

(1/33)

5

Risperidone

6%

(2/33)

M 1 D

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