Constipation in Hypercalcemia?

[eduro25]

Hi everyone. Does anyone know why Hypercalcemia causes constipation?. I mean I know its a frequent side effect of calcium channel blockers (less Ca , less contraction power) , but it just doesnt make sense to me why high Ca causes it?
I would be very grateful if someone could explain me that,
Regards,
Eduro

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[lakersbaby]

my understanding is that in hypercalcemia you get polyuria which leads to dehydration which in turn can lead to constipation

 

[Whats_up_doc]

Hi everyone. Does anyone know why Hypercalcemia causes constipation?. I mean I know its a frequent side effect of calcium channel blockers (less Ca , less contraction power) , but it just doesnt make sense to me why high Ca causes it?
I would be very grateful if someone could explain me that,
Regards,
Eduro

Hypocalcemia can give you constipation as well because of decreased muscle contractility.

 

[eduro25]

Thanks both for the answers.
Just one more question please Whats_up_doc , I searched the mechanism why hypercalcemia causes decreased muscle contractility (and hence constipation), but couldnt find a convincing explanation. Can you or anyone reading this please help me explaning me how?

Thanks in advance,

 

[Whats_up_doc]

Thanks both for the answers.
Just one more question please Whats_up_doc , I searched the mechanism why hypercalcemia causes decreased muscle contractility (and hence constipation), but couldnt find a convincing explanation. Can you or anyone reading this please help me explaning me how?

Thanks in advance,

I don't really know the answer to your question but I suppose it has to deal with the Myosin Light Chain Kinase Pathway...

 

[zenaku86]

Calcium has some depressive effect on the CNS that can lead to coma, confusion, somnolence, weakness. Gastrointestinal symptoms are related to the depressive action of hypercalcemia on the autonomic nervous system and resulting smooth-muscle hypotonicity.

Increased gastric acid (gastrin) secretion often accompanies hypercalcemia and may intensify gastrointestinal manifestations. Anorexia, nausea, and vomiting are intensified by increased gastric residual volume. Constipation is aggravated by dehydration that accompanies hypercalcemia. Abdominal pain may progress to obstipation and can be confused with acute abdominal obstruction.

Just to add, hypercalcemia can also cause acute pancreatitis. Studies suggest that hypercalcemia induces pancreatic injury via a 1.secretory block, 2.accumulation of secretory proteins, and possibly 3.activation of proteases.

(sorry bout the title, it is depressant effect not 'anti')

 

[illixir]

How does hypercalcemia cause polyuria again?

 

[zenaku86]

1. high concentration of calcium in the blood promote renal clearance thru osmotic diuresis leading to polyuria.

2. high calcium can cause renal impairment, thus further reducing water reabsorption

 

[turkeyjerky]

How does hypercalcemia cause polyuria again?

also causes nephrogenic diabetes insipidus via post-receptor resistance to ADH

 

[FutureDoc4]

Maybe I am missing some grandiose physiology concept however I thought it was much simpler than that:

Hypocalcemia, lowers the threshold for AP (Hence, Chvostek's sign) closer to the resting potential resulting in tetany.

Well, Hypercalcemia, moves the threshold for an AP (e.g. motor neurons, intestines) further away from resting potential (opposite direction). Leading to the intestines contracting less often (less peristalsis = constipation).

All of this of course is based on the Nerst equation. If someone wants to try and work out the math, I'll leave it to them.

 

[Aphtalyfe]

Maybe I am missing some grandiose physiology concept however I thought it was much simpler than that:

Hypocalcemia, lowers the threshold for AP (Hence, Chvostek's sign) closer to the resting potential resulting in tetany.

Well, Hypercalcemia, moves the threshold for an AP (e.g. motor neurons, intestines) further away from resting potential (opposite direction). Leading to the intestines contracting less often (less peristalsis = constipation).

All of this of course is based on the Nerst equation. If someone wants to try and work out the math, I'll leave it to them.

How does Hypercalcemia increase the magnitude of the membrane potential is the question.

If I increase the amount of a positive ion that normally wants to flow into the cell... that will cause a transient depolarization not hyperpolarization. This it seems would actually make muscle cells hypercontractile. (or possibly unable to repolarize)

So that cannot be the reason for the muscle's decrease in contraction.

The actual reason is that Calcium has an effect on sodium channels and lowers or increases their threshold for opening.

So for instance... If I have hypocalcemia my NaV gated channel threshold for opening goes from -60 to -70... so now my muscle cell will induce an AP much more easily. (Hypercontractile)

Conversely if I have hypercalcemia my NaV threshold for opening does from -60 to -50 thus making it more difficult for my cell to achieve an AP.

The numbers used are just for explaining the concept.

 

[anonymous000]

Hypocalcemia can give you constipation as well because of decreased muscle contractility.

you're an idiot.

hypocalcemia gives you increased contraction (leading to tetanus and diarrhea) and hypercalcemia induces flaccidity and constipation.

increased extracellular ca2+ levels --> increased diffusion of ca2+ into post-synaptic terminals prior to action potential --> reduced efficiency of ca2+ influx at post-synaptic terminals during action potential because electrical gradient is reduced --> decreasing acetylcholine release from these terminals --> muscle flaccidity. in the event of the smooth muscle of the intestine, this flaccidity reduces the rate of peristalsis --> constipation.

 

[bluesTank]

you're an idiot.

hypocalcemia gives you increased contraction (leading to tetanus and diarrhea) and hypercalcemia induces flaccidity and constipation.

increased extracellular ca2+ levels --> increased diffusion of ca2+ into post-synaptic terminals prior to action potential --> reduced efficiency of ca2+ influx at post-synaptic terminals during action potential because electrical gradient is reduced --> decreasing acetylcholine release from these terminals --> muscle flaccidity. in the event of the smooth muscle of the intestine, this flaccidity reduces the rate of peristalsis --> constipation.

FutureDoc4 above is right.

Anonymous is wrong. The electrical gradient is increased (not reduced). The resting potential is more positive, due to increased Ca2+ extracellularly, requires more Na to enter cell to reach the threshold. I don't even understand where you were going after that point...

 

[Slade]

FutureDoc4 above is right.

Anonymous is wrong. The electrical gradient is increased (not reduced). The resting potential is more positive, due to increased Ca2+ extracellularly, requires more Na to enter cell to reach the threshold. I don't even understand where you were going after that point...

people, people, no need for insults
Whats_up_doc probably meant "HYPERcalcemia" since that is what the OP was asking about

HYPERcalcemia: raises threshold for action potential -> decreased contraction -> constipation
HYPOcalcemia: lowers threshold for action potential -> increased contraction -> Chvostek's sign

 

[LinaHT]

How exactly hYPERcalcemia decreases AP threshold and contraction and vise and versa?!!
from what I know, Calcium is responsible for releasing Acetylecholine AP and contraction..

but i have a theory, MAYBE it causes hypercontraction. I mean like fibrillation in the cardiac muscles when there is too much signals reaching the muscle.

what do u guys think?

 

[LinaHT]

i mean increases AP threshold, sorry

 

[Guyton Killah]

Ouch. Get your facts right.

 

[unsung]

GI doc told us that dehydration has NOTHING whatsoever to do with causing constipation. Basically the idea being that what happens in the colon is not reflective of how much water you drink. I.e. drinking more water is not going to change what goes on in your colon.

(Sorta analogous to the idea that a "normal" person who eats more salt- like has a real salty meal one day, is NOT going to get hypertension from his diet, 'cuz his kidney is going to function normally and balance out the intake... this is my analogy, not his. lol)

Anyway, he was fairly emphatic about this point, saying that "even some of our nurses get this wrong and tell pts to drink more water".

I'm still not sure if I totally totally buy this, however. 'Cuz my internetz searches show a lot of sources claiming the opposite-- that water intake IS related to constipation.

Anyone confirm one way or the other???

 

[hyrule]

GI doc told us that dehydration has NOTHING whatsoever to do with causing constipation. Basically the idea being that what happens in the colon is not reflective of how much water you drink. I.e. drinking more water is not going to change what goes on in your colon.

(Sorta analogous to the idea that a "normal" person who eats more salt- like has a real salty meal one day, is NOT going to get hypertension from his diet, 'cuz his kidney is going to function normally and balance out the intake... this is my analogy, not his. lol)

Anyway, he was fairly emphatic about this point, saying that "even some of our nurses get this wrong and tell pts to drink more water".

I'm still not sure if I totally totally buy this, however. 'Cuz my internetz searches show a lot of sources claiming the opposite-- that water intake IS related to constipation.

Anyone confirm one way or the other???

don't drink water for a day and see how pooping goes

 

[LinaHT]

Ouch. Get your facts right.

what facts do u exactly mean?

cuz i know for sure that muscles need calcium to contract.

however, i read in wikipedia they say, hypercalcemia decreases neuromuscular excitibility and so decreases the contraction, i think it's something like tolerance.
and hypocalcemia makes the cell thinks that the muscle is depolarized so it spontanously generats action potentials and causes contarctions, this what happens whith hypocalcemic tetany.

i know there is a difference between skeletal and smooth muscles but the difference only in the mechanism, they both need calcium to contract but one through acetylecholine pathway and the other through actine and myosine.

 

[IandIatrogenic]

Well then GI Doc Needs to go back to his or her 1st year of physio...do not pass go do not collect a six figure paycheck a year for jamming endoscopes up patients' rectums because dehydration definitely can play a role in constipation.

But back to the question at hand. Whoever said that Hypercalcemia increased the threshold for neurons firing is correct. That would make presumably make the threshold MORE negative not less. The mechanism is via "guarding" of the voltage gated Na+ channels. Free Ca++ is increased and it is larger and has a more positive charged. From my understanding of what I've studied this is an actual physical obstruction of the channel.

Anonymous premed dufus doesn't know what he or she is talking about. He or she needs to stick to studying Newtonian Physics for the MCAT.

 

[veganbythefjord]

BUMP

 

[Ven0m]

BUMP

Kaplan physiology says there is always some Ca2+ blocking some fast Na+ channels on neurons at any given time. With that in mind, they said that hypercalcemia means more Ca2+ blocking Na+ channels (causing hypoexcitability, eg decreased muscle strength and mental depression), and hypocalcemia means less Ca2+ blocking Na+ channels (causing hyperexcitability, eg muscle spasms and seizures).

They didn't say explicitly state anything about hypercalcemia and constipation but it fits their rule.