Prep4USMLE Forum » USMLE Step 1 Forum » Physiology Forum |   Calcium Receptor mutation NBME F2 S2

Author	9 Posts
pearljam59 Forum Guru Topics: 120 Posts: 273	04/05/06 - 01:10 PM             #1 A 3-year-old boy has a mutation in the calcium receptors on cell surfaces of his parathyroid gland and on the basolateral (blood) side of the thick ascending limb of the loop of Henle. Which of the following patterns is expected with a mutation that leads to activation of this receptor in the absence of binding of its ligand? Ca++ Parathyroid hormone Urine calcium A ) Hypercalcemia high high B ) Hypercalcemia high low C ) Hypercalcemia low high D ) Hypercalcemia low low E ) Hypocalcemia high high F ) Hypocalcemia high low G ) Hypocalcemia low high H ) Hypocalcemia low low
robin082006 Forum Hero Topics: 471 Posts: 5,125	04/05/06 - 02:44 PM             #2 B ___________________ The Key to Succeed is Patience.
ralux Forum Senior Topics: 5 Posts: 59	04/06/06 - 07:06 AM             #3 e
ralux Forum Senior Topics: 5 Posts: 59	04/08/06 - 09:18 AM             #4 pearljam, whats the right answer?
pearljam59 Forum Guru Topics: 120 Posts: 273	04/08/06 - 05:54 PM             #5 Wow! I thought it was B and was typing a long explanation and then I reread the question and changed my mind. It is the calcium receptor ON the PT gland that is mutated and in a state of activation. So what it is doing is causing feedback inhibiton because the PT gland is tricked into thinking their is a ton of calcium. So that means you can become hypocalcemic (piss out all your calcium) and your body will not release PTH because it thinks their is alot of calcium so low PTH. Since PTH also acts in the early DCT to reabsorb calcium, the calcium will stay in the urine get excreted so high calcium in the urine. I go with G. Well my test is very soon and I could be delirious right about now so correct me if I am wrong.
USMLEGladiator Forum Guru Topics: 121 Posts: 411	04/16/06 - 04:36 AM             #6 yes, it is G ___________________ scores are just up to how high we aim and of course the amount of effort and time we put into it
krsna Forum Senior Topics: 1 Posts: 211	04/16/06 - 01:49 PM             #7 i go with G too...
vamsi2004 Forum Elite Topics: 7 Posts: 144	08/06/06 - 07:16 PM             #8 wats the correct ans - B or G?
rn Forum Senior Topics: 30 Posts: 80	08/07/06 - 04:07 AM             #9 good explanation pearljam.its G good luck

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