hyperparathyroidism...

[nisreen]

---

Members do not see this ad.

in a patient with hyperparathyroidism, what is most likely to be increased? :

renal calcium excretion or renal organic phosphate excretion?

this question is there in test packet I-L.. and the answer is given as renal calcium excretion...the other options given are :
1)intestinal calcium absorption,
2)intestinal organic phosphate absorption,
3)renal calcitriol production..

can someone please explain...

thanks...

 

[nisreen]

i figured out why renal organic phosphate excretion wouldnt be increased... 🙂

extracellular fluid contains inorganic phosphate and not organic... so its the inorganic form of phosphate which is excreted by the kidneys...and options 1 and 3 occur in a normal state.. so accordingly, renal calcium excretion would be the right answer...

 

[Boetlaar]

I'm pretty sure the key is wrong on this one (I came across it as well). Hyperparathyroidism is very straightforward in it effects...

1. increased bone resorption, allowing flow of calcium from bone to blood
2. reduced renal clearance of calcium (opposite of ans)
3. increased intestinal calcium absorption (should be ANS)

The only possible way that it could be right is if it is considering secondary which is due to a decrease in PTH sensitivity.

 

[nisreen]

although parathormone stimulates calcium absorption, calcium excretion is greatly elevated in primary hyperparathyroidism due to increase in filtered calcium load.The elevation of circulating active vitamin D conttributes to hypercalcemia and subsequently to hypercalciuria..

ref: Diseases of Kidney and Urinary Tract by Robert W. Schrier ( google book search)

 

[kuv101DDS]

I ran into a similar PTH question where I didn't agree with the given answer.
Do you guys agree with this statement:
Increased PTH levels will cause:
1 - an increase in Calcium and Phosphorous serum levels via bone resorption,
2 - an increase in phosphorous tubular excretion, and
3 - a decrease in phosphorous tubular reabsorption.

i'm getting this from the kaplan book and the USMLE first aid so let me know if i'm missing something.
thanks

 

[nisreen]

parathyroid hormane causes phosphate to be released from bone and it also inhibits tubular reabsorption of phosphorus...but i dont know if the serum phosphorus level increases

 

[cyberjockey123]

parathyroid and thyroid hormones act so as to maintain calcium homoestasis in the body......in hyperparathyroidism the calcium is increasingly being resorbed from the bones and it well exceeds its renal tubular secretion limit...so calcium is the answer

 

[docnc]

I ran into a similar PTH question where I didn't agree with the given answer.
Do you guys agree with this statement:
Increased PTH levels will cause:
1 - an increase in Calcium and Phosphorous serum levels via bone resorption,🙂
2 - an increase in phosphorous tubular excretion, and
3 - a decrease in phosphorous tubular reabsorption.

i'm getting this from the kaplan book and the USMLE first aid so let me know if i'm missing something.
thanks

effect on serum calcium:
It enhances the release of calcium from the large reservoir contained in the bones. Bone resorption is the normal destruction of bone by osteoclasts, which are indirectly stimulated by PTH. Stimulation is indirect since osteoclasts do not have a receptor for PTH; rather, PTH binds to osteoblasts, the cells responsible for creating bone. Binding stimulates osteoblasts to increase their expression of RANKL, which can bind to osteoclast precursors containing RANK, a receptor for RANKL. The binding of RANKL to RANK stimulates these precursors to fuse, forming new osteoclasts which ultimately enhances the resorption of bone.

effect on serum phosphrus:
PTH also enhances the uptake of phosphate from the intestine and bones into the blood. Slightly more calcium than phosphate is released from the breakdown of bone, and the intestinal absorption of phosphate (mediated by an increase in activated vitamin D) is not as dependent on vitamin D as is that of calcium.