Prolactin / Dopamine Flashcards
How is prolactin secreted?
Anterior pituitary gland (Lactotrophs) - synthesis prolactin
What is the function of prolactin? (2)
- stimulate breast development and stimulates milk production
How is prolactin release regulated?
Factors which increase/decrease prolactin release?
- Stimulate breast development and stimulates milk production
- Decreased GnRH pulsatility at the hypothalamic level
- blocks the action of LH on the ovary or testis
What is the process of prolactin on milk production?
- Development of mammary glands within breast tissues
- Prolactin promotes the growth of mammary alveoli, which are the components of the mammary gland, where the actual production of milk occurs.
- Prolactin stimulates the breast alveolar epithelial cells to synthesize milk components, in pregnancy
What is the physiology of prolactin release?
- Thyrotropin-releasing hormone (TRH) + dopamine are both released by the hypothalamus
- TRH is released by the hypothalamus and stimulates the release of both TSH and prolactin from the anterior pituitary.
- Dopamine has an inhibitory effect on prolactin release. When dopamine levels are high, it suppresses prolactin secretion.
- For TSH, dopamine inhibits its release by suppressing the production of thyrotropin-releasing hormone (TRH) in the hypothalamus.
- Both hormones modulate lactotophic activit
What is the mechanism of dopamine release?
- Dopamine is continuously secreted by **dopaminergic neurons **that project from the arcuate nucleus of the hypothalamus into the anterior pituitary gland via infundibulum.
- The dopamine that is released at the terminal buttons of the nerves, acts on lactotrophs - Inhibiting prolactin synthesis
- In the absence of pregnancy (i.e., high estrogen) or lactation in sexually mature females, prolactin is constitutively inhibited by dopamine,
What is the pathophysiology behind medications cause hyperprolactinaemia?
Medications that antagonize dopamine production
* ** antipsychotics** or masses that compress the infundibulum
* disrupt the basal inhibition of prolactin synthesis
* resulting in hyperprolactinemia.
Which drugs can be used to treat hyperprolactinaemia?
- Dopamine agonists
* bromocriptine
* cabergoline
inhibit prolactin secretion and can be used to treat pathologies associated with hyperprolactinemia
What is the most potent stimulation for prolactin synthesis?
Suckling or nipple stimulation; most potent stimulator for prolactin synthesis
1. This mechanical process stimulates sensory nerve to the hypothalamus
2. - which inhibits dopamine release
removing the inhibitory action of dopamine on prolactin.
Why does hyperprolactinaemia lead to amenorrhea?
Prolactin inhibits the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus
- The loss of GnRH results in a lack of pulsatile stimulation of gonadotrophic cells resulting in the loss of FSH and LH release from the anterior pituitary.
- FSH and LH are the primary hormones needed to regulate menstruation
- thus, females who are lactating will experience a period of transient amenorrhea until the cessation of breastfeeding.
Which drugs can lead to hyperprolactinaemia?
Drugs - metoclopramide, domperidone, haloperidol
- Inhibits dopamine production, dopamine receptor antagonists, synthesis inhibitors and pituitary overproduces prolactin
What are the other causes of hyperprolactinaemia?
- Prolactinoma
- Pregnancy
- Drugs - metoclopramide, domperidone, haloperidol
- Inhibits dopamine production, dopamine receptor antagonists, synthesis inhibitors and pituitary overproduces prolactin
What are the clinical features of hyperprolactinaemia?
- Hypogonadism - infertility, impotence, decreased libido
- Gynocomastia and galactorrhea
- Amenorrhea
- Visual impairment, headaches - when pituitary adenoma presses on optic nerve
What are the investigations indicated with hyerprolactinaemia?
- Head MRI
- Lab results - high serum prolactin
What is the management of hyperprolactinaemia?
Dopamine agonist - Bromocriptine/Cabergoline
Surgery - sx removal of tumor
