auto antibody 1001 series

[pizza1994]

A male with serum auto-antibodies that bind to the thyroid gland TSH receptors should be considered as:

a) healthy, because negative feedback will regulate the level of thyroid hormone

b) having low levels of thyroid hormone because autoantibodies block TSH from binding to its receptor

c) having high levels of thyroid hormone because autoantibodies are overstimulating the thyroid gland

d) having low levels of thyroid hormone because autoantibodies are destryoing the thyroid gland

i dont get this. doesnt auto-antibody destroy your own receptors?

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[Sed8&Intub8]

I think C??

 

[IslandStyle808]

I going to pick B on this one (not sure). My reasoning is that antibodies normally neutralize what they attach to, so in this case it is blocking TSH or any other hormone that attaches to the receptors on the thyroid.

 

[Apoplexy__]

Should be C. They're referring to Graves' disease. The autoantibodies stimulate the TSH receptor, not destroy/block it.

I have no idea how they expected a pre-med student to know this...

 

[sillyjoe]

Should be C. They're referring to Graves' disease. The autoantibodies stimulate the TSH receptor, not destroy/block it.

I have no idea how they expected a pre-med student to know this...

@kirbymiester is on the money. This is absolutely out of scope for the MCATs because antibodies can both inactivate or activate (as in the case) a receptor depending on the specific scenario. There are pharmacological examples like Rituximab (a monoclonal antibody) which is used to treat certain forms of lymphoma's by binding and inactivating certain receptors on B-cells. They cannot expect you to know which instances they inhibit and which instances they activate. Therefore, this is an absolutely terrible question for the MCAT.

However, you can still take it as a helpful piece of information that you can now have just in case the MCAT does ask a crappy question !

 

[Czarcasm]

Should be C. They're referring to Graves' disease. The autoantibodies stimulate the TSH receptor, not destroy/block it.

I have no idea how they expected a pre-med student to know this...

Yeah, it is C (Grave's Disease). Only way I knew this was from my Immunology class. It was one of the classic hypersensitivity reactions (I believe type II); In this case an antibody stimulates a receptor and keeps it turned on. Unless it was presented in a passage, I don't think this is common knowledge expected of you.

 

[orangetea]

Yeah, it is C (Grave's Disease). Only way I knew this was from my Immunology class. It was one of the classic hypersensitivity reactions (I believe type II); In this case an antibody stimulates a receptor and keeps it turned on. Unless it was presented in a passage, I don't think this is common knowledge expected of you.

yes!! I remember this from Immuno as well.

The test writer must've felt super awkward after writing this question (if it was a stand alone).

 

[mcloaf]

I have no idea how they expected a pre-med student to know this...

Seriously.

 

[Mantis Toboggin]

I understand that this is out of the scope of the MCAT but here is my question.

The antibodies are recognizing the tsh receptors as antigens, right? Shouldn't there be an autoimmune reaction that attempts to destroy cells with tsh receptors?

Related, how do we know that the binding of the antibody at the receptor will mimic the effect of tsh? Is this according to the induced fit theory?

 

[sillyjoe]

I understand that this is out of the scope of the MCAT but here is my question.

The antibodies are recognizing the tsh receptors as antigens, right? Shouldn't there be an autoimmune reaction that attempts to destroy cells with tsh receptors?

Related, how do we know that the binding of the antibody at the receptor will mimic the effect of tsh? Is this according to the induced fit theory?

This is exactly why it is out of scope. Some antibodies can bind and stimulate a receptor by acting as a substrate and some can cause an autoimmune response. You will learn the details when you get to medical school