Prolactin Flashcards
Where is PRL synthesized?
In lactotropes which make up about 20% of anterior pituitary cells.
What common precursor do lactotropes and somatotropes share?
A precursor cell that may give rise to a tumor secreting both PRL and GH.
What are normal serum PRL levels in adults?
10–25 g/L in women and 10–20 g/L in men.
When are PRL secretion peaks highest?
During REM sleep with peak serum PRL levels up to 30 g/L occurring between 4:00 and 6:00 A.M.
What is the half-life of circulating PRL?
About 50 minutes.
How is PRL secretion controlled?
By tonic inhibition via dopamine acting on D2 receptors and stimulated by TRH and vasoactive intestinal polypeptide.
What is PRL’s primary function?
To induce and sustain lactation.
How do estrogen and progesterone affect lactation?
They inhibit lactation during pregnancy but their rapid decline postpartum allows lactation to occur.
What factors can transiently raise serum PRL levels?
Exercise meals sexual intercourse minor surgeries general anesthesia acute myocardial infarction and acute stress.
What are natural causes of increased PRL secretion?
Pregnancy lactation and chest wall stimulation.
What conditions can cause stalk damage leading to hyperprolactinemia?
Tumors such as craniopharyngioma and meningioma as well as trauma.
What pituitary conditions can cause excess PRL secretion?
Prolactinoma and acromegaly.
What systemic conditions are linked to hyperprolactinemia?
Chronic renal failure hypothyroidism and cirrhosis.
What types of drugs can cause hyperprolactinemia?
Dopamine receptor blockers like phenothiazines thioxanthenes and metoclopramide dopamine synthesis inhibitors like α-methyldopa H2 antagonists like cimetidine and ranitidine and calcium channel blockers.
What are the hallmark symptoms of hyperprolactinemia in women?
Amenorrhea galactorrhea and infertility.
What happens if hyperprolactinemia occurs before menarche?
It causes primary amenorrhea.
What are the common symptoms of hyperprolactinemia in men?
Diminished libido infertility and visual loss from optic nerve compression.
What is galactorrhea?
Inappropriate milk discharge from the breast considered abnormal if it lasts longer than 6 months postpartum.
How is galactorrhea related to acromegaly?
About one-third of acromegaly patients experience galactorrhea.
When should plasma PRL be measured in women?
In cases of amenorrhea regardless of galactorrhea presence.
What should be included in the patient history?
Medication use symptoms of pituitary mass effects and hypothyroidism.
What PRL levels suggest a prolactinoma?
Levels above 200 ng/mL indicate prolactinoma levels between 100 and 200 ng/mL strongly suggest it while levels below 100 ng/mL may be due to other causes.
When is testing for hypopituitarism needed?
Only in patients with macroadenoma or hypothalamic lesions.
Why is pituitary imaging recommended?
To rule out nonfunctional pituitary or hypothalamic tumors.
Why are most patients treated for microadenomas and idiopathic hyperprolactinemia?
To address infertility and prevent estrogen deficiency and osteoporosis.
What are the first-line treatments for microadenomas and idiopathic hyperprolactinemia?
Dopamine agonists like bromocriptine and cabergoline.
When is transsphenoidal surgery used for microadenomas?
In rare cases where patients do not respond to or cannot tolerate dopamine agonists.
What is the first-line treatment for prolactin-secreting macroadenomas?
Dopamine agonists which normalize PRL levels shrink tumors and improve vision in 90% of cases.
What should be done if mass effects are present in macroadenomas?
Increase the dopamine agonist dose gradually over several weeks.
When should visual field tests be repeated in macroadenomas?
4-6 weeks after starting therapy if they were initially abnormal.
When should pituitary imaging be repeated in macroadenomas?
3-6 months after starting therapy.
When is transsphenoidal surgery indicated for macroadenomas?
If the tumor does not shrink or if visual field abnormalities persist despite dopamine agonist therapy.
