QuestionSBA
QuestionChoice
FGF23 **decreases** the serum levels of Vitamin D3. FGF23's main job is to decrease serum phosphate. Vitamin D3 on the other hand increases serum phosphate by stimulating uptake in the small intestines, and reabsorption in the kidneys.

FGF23 blocks the production of Vitamin D3 to prevent its effect on phosphate reabsorption - therefore, it **decreases** serum Vitamin D3.
10001834
c
Increases serum Vitamin D3 levels
QuestionChoice
The main job of FGF23 in the body is to promote the excretion of phosphate through the urine by inhibiting the sodium-phosphate co-transporter found in the proximal convoluted tubule.

It also inhibits the production of calcitriol (Vitamin D3), which has a potent effect of causing phosphate reabsorption in the kidneys and bowels - which FGF23 is trying to stop.
10001832
a
Reduces serum phosphate
QuestionChoice
FGF23 is responsible for regulating serum phosphate levels in the body (lowering serum phosphate levels) - it does not affect serum potassium levels.
10001836
e
Decreases serum potassium levels
QuestionChoice
FGF23 does the exact opposite - its main role is to **decrease** the serum phosphate in the body.

It does so by increasing the excretion of phosphate through the urine and decreasing the levels absorbed from the kidneys and bowels (which it does by inhibiting the production of Vitamin D3).
10001833
b
Increase serum phosphate
QuestionChoice
FGF23 blocks the production of Vitamin D3 to prevent its effect on phosphate reabsorption.

Vitamin D3 is responsible for increasing the levels of calcium absorption in the body. Therefore, a decrease in the levels of Vitamin D3 would cause a **decrease** in serum calcium levels.
10001835
d
Increases serum calcium levels
Concept
Chapter
2693
3978
Calcium homeostasis
Topic
133
Endocrinology
12913
What is the role of the hormone fibroblast growth factor 23 (FGF23) in the human body?
a