NBME 23 Inorganic phosphorus: decreased;<br />Parathyroid hormone: increased;<br />Calcitriol: decreased (NBME Answers)

need help with your account or subscription? click here to email us (or see the contact page)

search for anything ⋅ score predictor (“predict me!”)

NBME 23 Answers

nbme23/Block 4/Question#3 (reveal difficulty score)
A 33-year-old woman comes to the physician ...
Inorganic phosphorus: decreased;
Parathyroid hormone: increased;
Calcitriol: decreased 🔍 / 📺 / 🌳 / 📖
tags:

+9 upvote downvote
submitted by ∗lfsuarez(160)

get full access to all content ⋅ pick a username

Answer E

Inorganic Phosphorus ; Parathyroid Hormone ; Calcitriol

Decreased ; Increased ; Decreased

This patient is suffering from celiac sprue, which in this case has caused Vitamin D malabsorption and therefore decreased serum calcium. The body will respond to the decreased calcium via secretion of PTH. This will then cause phosphorous wasting to occur in the proximal convoluted tubule.

get full access to all content ⋅ pick a username

kuhnboom Why does Calcitriol not increase with the increased PTH? Wouldn't the increased PTH stimulate the kidneys to make more activated vitamin D. +2

batmane vitamin d malabsorption --> dec calcitriol +6

peridot @kuhnboom Yes, while PTH stimulates the kidneys to make more active vitamin D (calcitriol), you need vitamin D precursors to begin with in order to do that. If you have vitamin D malabsorption, then the activated form won't be high even with high levels of PTH. Therefore, calcitriol is decreased. +

cbreland Also, Vitamin D causes Ca and Phosphate absorption in the intestines. A lack of activated vitamin D would cause more Ca/Phosp wasting +

iwannabedonewiththis Uworld ID: 981 +

+1 upvote downvote
submitted by ∗lumd(4)

get full access to all content ⋅ pick a username

Celiac sprue → fat malabsorption → Decreased ADEK vitamins

Decreased Vit D (Calcitriol) → decreased Ca2+ reabsorption (which 80% is reabsorbed from intestines) → decreased serum Ca2+ → increased PTH → increased renal excretion of Phosphate → decreased serum Phosphorus

get full access to all content ⋅ pick a username

Must-See Comments from nbme23

ferrero on Precapillary resistance
yotsubato on 99%
sne on Triglyceride
sajaqua1 on Area labeled ‘D’ (Spinothalamic tract, right)
stinkysulfaeggs on Hypoglycemia
hayayah on Iris
soph on Peak inspiratory pressure (alveolar): ...
seagull on Area labeled ‘C’ (Cranial nerve 8: ...
water on Dietary change
wired-in on 28.8
beeip on Binding of permeable ligand to nuclear ...
thomasalterman on Hypoglycemia
yotsubato on Inhibition of the cytochrome P450-dependent ...
seagull on Decreased sodium bicarbonate reabsorption in ...