Question 28

[Guest]

We know that calcitonin will lower blood calcium level, but how do we know that it will lower the blood calcium exactly to the normal level?

[matthew]

Homeostasis is the goal.

[admin]

Exactly: homeostasis. Answer choice C (the idea that the Ca levels would decrease) is only true up to a point. Once levels are normal, it would no longer decrease. Thus answer choice A is the best answer.

[briandgoudy]

wouldn't the body of a hypercalcemic individual already be producing calcitonin? In which case introducing exogenous calcitonin would initially shift plasma levels of calcium below normal.

[admin]

[aop50198527]

I heard that calcitonin has a very minimal effect on humans, as compared to other mammals and other Ca regulating hormones. I dont see how it can possibly be assumed that a complete return to normal ca levels will occur just by calcitonin.

[jellywing_2058]

First, that knowledge is not required for the question, though it is true that calcitonin does not have a very big impact on calcium regulation. However, calcitonin still does lower the calcium level in blood in the end.

[phoenixwarlord]

coming from a pharmacology background..i think in this case when the dosage of calcitonin given is not specified, it is only safe to say that calcium levels is reduced (choice C doesn't say it's reduced "below" normal, just reduced comparing to before), choice A is too specific for mcat imo, if the dosage given is not sufficient then there's no guarantee it'll for sure return to normal

[jays5558399]

[jellywing_2058]

The answers have been modified for clarification. Hope this helps!

[quadalpha]

[dnpgr16513]

Tricky..

[mohsinalam5969]

Calcitonin is a 32-amino acid linear polypeptide hormone that is produced in humans primarily by the parafollicular cells (also known as C-cells) of the thyroid, and in many other animals in the ultimobranchial body. It acts to reduce blood calcium (Ca2+), opposing the effects of parathyroid hormone (PTH). It has been found in fish, reptiles, birds, and mammals. Its importance in humans has not been as well established as its importance in other animals, as its function is usually not significant in the regulation of normal calcium homeostasis.
SO ACCORDING TO THIS MY PERSONAL BELIEF IS THAT OPTION C IS THE BEST BECAUSE OF THE LINE "ITS FUNCTION IS NOT USUALLY SIGNIFICANT IN THE REGULATION OF NORMAL CALCIUM HOMEOSTASIS"

[mohsinalam5969]

Calcitonin is a 32-amino acid linear polypeptide hormone that is produced in humans primarily by the parafollicular cells (also known as C-cells) of the thyroid, and in many other animals in the ultimobranchial body. It acts to reduce blood calcium (Ca2+), opposing the effects of parathyroid hormone (PTH). It has been found in fish, reptiles, birds, and mammals. Its importance in humans has not been as well established as its importance in other animals, as its function is usually not significant in the regulation of normal calcium homeostasis.
SO ACCORDING TO THIS MY PERSONAL BELIEF IS THAT OPTION C IS THE BEST BECAUSE OF THE LINE "ITS FUNCTION IS NOT USUALLY SIGNIFICANT IN THE REGULATION OF NORMAL CALCIUM HOMEOSTASIS"

[gotemrecor5286]

C is definitely the answer. It does not state how much calcitonin is given. Sometimes a dose large enough can be given to a patient where the calcium levels dip below normal levels. This is definite a bad question, not MCAT worthy.