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38 Cards in this Set

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Prolactin has the most sequence homology with what other hormone?
92% sequence homology with GH.
What are the functions of Prolactin?
1. Growth of breast tissue
2. Production of breast milk and secretion into alveoli
What stem cell are pituitary lactotropes derived from?
From the same stem cell as somatotropes--somatomammotrope.
Why does the pituitary size increase during pregnancy?
As a result of increased size and number of lactotropes.
Besides the pituitary, where else is prolactin synthesized?
The Endometrium, and secreted into amniotic fluid--may play a role in osmoregulation of amniotic fluid.
What is Little PRL?
An isoform of PRL--it is a non-glycosylated monomer w/ high bioactivity & immunoreactivity.
What is G-PRL?
Glycosylated PRL w/ decreased bioactivity and immunoreactivity.
What is Big PRL?
An isoform of PRL--it is a mixture of di- and trimeric G-PRL. It has decreased receptor binding.
What is Big-big PRL?
Probably G-PRL coupled w/ IgG. It has decreased receptor binding.
Can galactorrhea be present in the absence of hyperprolactinemia?
Yes
What is the predominate regulation of prolactin secretion?
Hypothalamic inhibition.
What is the main prolactin inhibiting factor?
Dopamine
What are additional PRL inhibiting factors?
1. Serotonin
2. TRH
3. Vasoactive Intestinal Protein (VIP)
4. Angiotensin II
5. Opioids
How does estrogen affect PRL?
It increases PRL synthesis and release; it is anti-dopaminergic
How do glucocorticoids affect PRL?
They decrease PRL gene transcription.
When do PRL levels rise during pregnancy?
Soon after implantation
Why doesn't lactation occur during pregnancy?
Progesterone decreases expression of PRL receptors in breast.
What happens to estrogen and PRL levels postpartum?
They fall significantly
When are the highest PRL levels?
During nocturnal sleep
When are the best times for PRL levels?
Early moring (around 3 am) and during fasting
What are some other conditions assoc w/ increased PRL release?
Sleep, food, stress, orgasm, breast stimulation
What are some central causes of inappropriate PRL secretion?
1. Hypothalamic
2. Pituitary
What are some specific pituitary problems that cause inappropriate PRL secretion?
1. Adenoma
2. Empty Sella Syndrome?
What's a pituitary adenoma?
A tumor that usually secretes PRL (prolactinoma); PRL secretion can also be assoc w/ GH secreting adenomas and ACTH adenomas.
What are the the types of prolactinomas?
1. Microadenoma (<10mm)
2. Macroadenoma (>10mm)
What are peripheral causes of hyperprolacinemia?
1. Hypothyroidism
2. Chest Wall Reflex (Surgery, Herpes Zoster)
3. Renal Failure (dec clearance)
4. Ectopic Production
What are some pharmacologic agents that increase [PRL]?
1. Anesthesia
2. Psychoactive agents (neuroleptics, TCAs, amphetamines, etc.)
What are some consequences of hyperprolacinemia?
1. Mastalgia
2. Menstrual abnormality (hypoestrogenism)
3. Hyper-androgenism
4. Insulin resistance
What does increased hypothalamic DA do?
Activates opioidergic neuronal activity and decreased GnRH pulsatility, causing menstrual abnormalities.
Women with amenorrhea and hypoestrogenism typically have what?
Increased PRL
When should you draw blood for lab analysis of PRL level?
In the morning after fasting
What are the most common type of PRL secreting tumor?
Microadenomas
What's a good imaging study to perform?
CT Scan -- possible to distinguish 2 mm lesions (good info about sella turcica)
What kind of course to microadenomas follow?
A benign course; studies demonstrate stability and slow growth.
Is therapy necessary for a microadenoma?
No, unless pregnancy is desired, hypoestrogenemia exists, or galactorrhea is troublesome.
What is the treatment of choice for a macroadenoma?
A dopamine agonist (bromocriptine) for six months.
Can bromocriptine be used in pregnant women w/ PRL-secreting tumors?
Yes, it's safe and doesn't cross placenta.
Is breast-feeding contraindicated in pts w/ PRL-secreting tumors?
No, unless patient is symptomatic.