PTH, Calcitonin, Vit D

Question 1

There are 2 types of cells in the parathyroid gland. What are they and what are their products?

Answer 1

Chief cells - PTH

Oxyphil cell - function unknown

Question 2

What is the effect of PTH? How is this accomplished (2)?

Answer 2

Increase blood calcium
Increase calcium and phosphate resorption
Decrease calcium secretion

Question 3

What are the effects of PTH on blood phosphate levels? How is this accomplished?

Answer 3

Decreased blood phosphate

Increase renal excretion

Question 4

What are the 2 phases of bone resorption mediated by PTH?

Answer 4

Rapid - PTH activation of osteoblast/cytes to get calcium from bone fluid (Ca++ only)
Slow - Indirect activation of osteoclasts to resorb bone (Ca++ and PO4)

Question 5

How are Osteoclasts activated to resorb bone?

Answer 5

Paracrine activation by osteoblasts

Question 6

What are the effects of PTH in the intestines?

Answer 6

Increased Ca++ adnd PO4 absorption from the intestines

Question 7

What is the major means of PTH regulation?

Answer 7

Ca++ in the blood. Sensed by GPCR on chief cells. Activation leads to PTH inhibition

Question 8

What is the effect of mutant GPCR on the chief cells preventing Ca++ binding?

Answer 8

Familial hypercalcemia

Question 9

Hypoparathyroidism is a disease of too little PTH. Symptoms include (3)

Answer 9

Decrease muscle excitability
Increased neuromuscular excitability (tingling in fingers/toes)
Carpopedal tetany - spasm of wrist, ankle, throat

Question 10

Hypoparathyroidism is treated with _

Answer 10

Vit. D and exogenous calcium

Question 11

The major effect of hyperprarthyroidism is _

Answer 11

Hypercalcemia

Question 12

Osteitis fibrosa Cystica is _

Answer 12

Disease of excessive bone resorption

Question 13

An important diagnostic indicator of hyperparathyroidism is (2). What is a clinical finding?

Answer 13

Increased alkaline phosphatase activity
Increased urinary cAMP
Increase calcium oxalate / phosphates stones

Question 14

The parafollicular cells of the thyroid make _. Its function is _

Answer 14

Calcitonin

Weak opposing effects to PTH

Question 15

How does calcitonin decrease blood phosphate levels?

Answer 15

By inhibiting bone resorption

Question 16

What other peptide is on the same gene as calcitonin?

Answer 16

CGRP

Question 17

2 sources of vit D are _

Answer 17

Skin

Diet

Question 18

What is the active form of vit D? inactive form? Where is it made?

Answer 18

1,25-Vit D
24,25 Vit D
both made in the kidney

Question 19

What is cholecalciferol? Where is it made?

Answer 19

Precursor to active vit D.

Kidney

Question 20

How is the active form of Vit D transported in the blood?

Answer 20

Bound to transcalciferin

Question 21

What is the effect of Vit D on intestinal calcium absorption?

Answer 21

Increases transcellular (not paracellular) by increasing calbindin expression which buffers intracell. Ca++ so more can enter cell

Question 22

What is the effect f high Vit D on bone? I

Answer 22

Increases bone resorption by binding osteoblasts

Question 23

A vit. D deficiency in children leads to _

Answer 23

Rickets

Question 24

A vit D deficiency in adults leads to _

Answer 24

Osteomalacia

Question 25

What is renal rickets?

Answer 25

Cant generate active vit D

Question 26

What is congenital hypophosphatemia?

Answer 26

Vit D resistant rickets, kidneys can’t absorb enough phosphate