Can someone help me with this question? NBME 16 - nathaliaray

[ArchivalUser]

A 35-year-old man comes to the physician because of a 3-year history of an enlarging nose, coarsening of his facial features, muscle weakness, and increased hand and foot size. Physical examination shows a large fleshy nose and prognatism. Serum studies show an increased insulin-like growth factor-I concentration. An MRI of the brain shows a pituitary adenoma. Morphologic analysis of a biopsy specimen of the tumor shows a densely granulated somatotroph adenoma. Further studies show that S subunit of G proteins in the tumor lack GTPase activity. The tumor cells in this patient most likely have an increased activity of wich of the following enzymes?

a) adenylyl cyclase
b) guanylyl cyclase
c) janus kinase
d) phospholipase C
e) Tyrosine kinase

the correct answer is A, but I can't understand why

[ArchivalUser]

This is acromegaly. Excess GH in adults typically caused by pituitary adenoma (somatotrophic adenoma). Serum studies show an increased insulin-like growth factor-I concentration- used for diagnosis of acromegaly. Read up on acromegaly in first aid in endocrine section page 341 in first aid 2018. Anyways, GHRH is part of cAMP in the signaling pathway of endocrine hormones. cAMP is part of G protein linked second messangers (pharmacology section in fa 2018 pg 234). cAMP has to do with Gs/Gi pathway which activates or inhibits adenylyl cyclase therefore increases or decreases ATP and thereafter cAMP and ultimately Protein Kinase A.

Sorry for the confusing explaination hope you understood

[ArchivalUser]

If you are struggling with biostatistics and epidemiology questions, please talk to us. We can explain these disciplines to you in a very easy way.

[ArchivalUser]

Thank you so much! The explanation is perfect!