Endo: Prolactin

What is the function of prolactin? (2)

• Enhance breast development during pregnancy

• Induce lactation

What affects the production of prolactin? (5)

• Pulsatile

• Increases with

  • Sleep

  • Stress

  • Pregnancy

  • Chest wall stim or trauma

Where does prolactin bind?

• Receptors in gonads, lymphoid cells and liver

How is the secretion of prolactin controlled? (2)

• Inhibitory control by dopamine- acts on D2 type receptors located on lactotrophs

What is prolactin release stimulated by?

Thyrotropin-releasing hormone.

What are the symptoms of hyperprolacinaemia in women? (4)

• Oligomennorhoea

• Amennorhoea

• Galactorrhoea (breast milk production)

• Infertility

What are the symptoms of hyperprolactinaemia in men?

• Sexual dysfunction

• Galactorrhoea

• Visual problems

• Headache

What symptom appears in both sexes?

• Tumor mass effects causing visual-field defects or headaches

What might cause hyperprolactinaemia? (5)

• Hypothalamic dopamine deficiency

• Defective transport mechanisms

• Lactotroph Insensitivity to Dopamine

• Stimulation of lactrotrophs

• Prolactinomas

What might cause Hypothalamic dopamine deficiency? (2)

• Disease of hypothalamus- tumor

• Some drugs- alpha methyldopa

What might cause defective transport mechanisms of prolactin? (1)

• Pituitary tumor

What might cause lactrotroph insensitivity to dopamine? (2)

• Dopamine antagonist medication- antipsychotics, antiemetics

What might cause stimulation of lactotrophs? (4)

• Hypothyroidism - increased TRH production

• Osterogens

• Injury to chest wall

• Abnormal stimulation of suckling reflex.

What difference is there between sexes and the prolactinoma types?

• In women with prolactinomas- 90% present with microprolactinomas (<10mm)

• Of men with prolactinomas, 60% present with macroprolactinomas (>10mm)

What pre-testing variables must be considered before testing for prolactinoma? (8)

• Pregnancy

• Drug history

• TFTs (hypothyroidism)

• Protein meal

• Exercise

• Chest wall injury

• Renal failure

• Cirrhosis

What is macroprolactin?

• Big big prolactin

• Monomer of prolactin and Ig molecule - prolonged clearance rate

What are the symptoms of macroprolactinoma?

• Macroprolactinoma has low biological activity and most patients do not present with symptoms (they still can present with symptoms of prolactinoma)

How is macroprolactin measured? (2)

• Separated from other forms by

  • Gel filtration chromatography (expensive)

  • Polyethylene glycol precipitation

How does PEG work?

• Seperates proteins based on soluability by removing solvent availability.

• PEG relatively specific for IgG and complexes

• PEG-treated sample analysed for prolactin

What are the results in PEG analysis of macroprolactin? (3)

• %80> recovery - No significant level of macroprolactin recovered.

• 60-80% - low levels

• <60% - Moderate to high

What is the treatment of prolactinoma? (3)

• Pharmacotherapy- dopamine agonists

• Surgical resection

• Radiotherapy