Physiology Flashcards
While looking at some lab values for your m patient you notice elevated MAO levels. Which physical features would this most likely be related to?
A. gynacomastia
B. hirsutism
C. hypothyroidism
D. exopthalmos
A gynacomastia
High levels of MAO (monoamine oxidase) leads to breakdown on monoamine such as the catacholamines (dopamine, epi, NE)
Decreased dopamine will decrease prolactin inhibition leading to high levels of prolactin and gynacomastia in men.
Your 33 y/o f patient recently came out of the ICU for treatment of serious burns on her abdomen, chest and face. Not long after she came to see you and mentioned she’s been having some nipple discharge, though she’s not pregnant. What is this an example of?
A. neg feedback loop
B. pos feedback loop
C. Adenohypophyseal reflex
D. Neurogenic reflex
Neurogenic reflex
Commonly due to nipple stimulation in non pregnant women, but can also occur with chest wall injury, burns, surgery, HSV in thoracic dermatomes.
These responses will only be eliminated with denervation of the nipple or spinal cord lesion.
How is estrogens role related to prolactin? What is the nature of their relationship during pregnancy?
High estrogen will stimulated hyperplasia of mammotrophs and transcription of PRL
Increases mammotroph sensitivity to PRL, decreases sensitivity to dopamine inhibition.
During pregnancy high estrogen and progesterone levels inhibit milk production. Only when they decrease following parturition does the crying and suckling baby lead to a neurogenic reflex stimulating milk produciton.
You have a 25 y/o m patient come to the clinic with his wife to discuss the trouble they’re having getting pregnant. His wife has been found to be healthy and fertile, but now the attention is on the husband. Upon physical exam you notice he has some hypogonadism and some rounding of his breasts. He also admits to a low libido and worries that he hasn’t been having sex with his wife enough to get her pregnant. Assuming he has an increase in prolactin secretion, what’s the reason for his decreased fertility?
A. prolactin decreased testosterone by decreasing TSH
B. prolactin causes breast development and high estrogen secretion making him infertile
C. They’re unrelated and he likely has a prolactinoma
D. prolactin inhibits GnRH which will decrease fertility by decreasing release of LH and FSH.
D. prolactin inhibits GnRH which will decrease fertility by decreasing release of LH and FSH.
This same mechanism will decrease ovulation and fertility in females and is the reason why breast feeding female are less likely to get pregnant.
What role does prolactin play in breast development? Which one of these roles is inhibited during pregnancy?
Stimulates branching and proliferation of ducts.
It also induces transcription of enzymes needed for the biosynthesis of lactose, casein, and lipids.
This second function is inhibited during pregnancy
What are some reasons for an excess or loss of dopamine?
Excess dopamine: drugs (L-dopa, parkinsons), increase in prolactin (prolactinoma) will stimulate dopamine increase as part of neg feedback, hypothalamus excessive dopamine release
Damage to the pituitary stalk: increase PRL, increase dopamine (decrease its effect). Increase number of lactotrophs via estrogen: increase PRL, increase dopamine, but inhibition will be escaped by PRL in a similar manner as a prolactinoma. Decrease in MOA. Dopamine agonists.
Loss: Loss of lactotrophs, decrease prolactin release and decrease stimulation of dopamine. Increased monoamine oxidases.
Sometimes prolactinomas secrete more than just prolactin, but also another similarly structured hormone. What is it?
GH
What is dopamines effect on lactotrophs within sec, min-hrs, and days?
sec: hyperpolarize cells, decrease VG Ca2+ channels, Decrease Ca2+ intracellularly which stops PRL secretion
Min-hrs- decrease in adenylyl cyclase activity and thus decrease in cAMP and the effect this second messanger has on PRL secretion
Days- decrease in lactotroph hyperplasia and hypertrophy
When are prolactin and GH released?
Prolactin increases 1-2 hrs after sleep begins
GH sleep stages 3-4
Your patient is diagnosed with primary hypothyroidism but is showing signs of hyperprolactinemia; why?
The decreased release T3/T4 by the thyroid will decrease the neg feedback on the hypothalamus. TRH and TSH will increase in response but instead of having an effect on T3-T4 secretion the TRH will increase prolactin secretion and over ride the primary regulator (dopamine).
Oxytocin acts on which part of the breast? What’s it’s function? Prolactin?
Oxytocin- Lobes (myoepithelial cells) cause milk ejection
Prolactin- Lobes alveolar cells cause milk production
Why does GH stimulated hyperglycemia?
GH trying to keep sugar in the blood to feed the brain, especially during times of starvation.
Which effect is stronger, and which is dominant? GHRH vs somatostain
GHRH is domanant because there is more of it, but somatostain has a stronger effect. Under normal conditions GHRH acts to release GH.
Name two inhibitors of the Na/I transporter in follicular cells of the thyroid
Perchlorate, and thiocyanate
Following hydrolysis of T3 and T4 from TG what happens to MIT and DIT each?
T4 (majority) and T3 hitch a ride on thyroxine binding globulin to travel in the blood to peripheral tissue. T4 is converted to T3 there via 5’ deiondinase.
MIT and DIT are deionidinzed as well and the Iodine and tyrosine are recycled.
