Endocrine 10: Calcitonin + tetany

Question 1

Cells secreting Calcitonin

Answer 1

Parafollicular cells of thyroid gland

Question 2

Nature of Calcitonin

Answer 2

Polypeptide (32aa)

Question 3

General function of Calcitonin

Answer 3

Hypocalcemic

Question 4

effect of Calcitonin on bones

Answer 4

It decreases overall mobilisation of calcium from the bones:
* decrease the number and activity of osteoclasts
* increase osteoblasts and it’s alkaline phosphatase
* inhibits calcium pump of osteocytic membrane

Question 5

effect of Calcitonin on Kidney

Answer 5

• Inhibits, alpha one hydroxylase, enzyme leading to less vitamin D synthesis
• increases excretion of calcium and phosphate

Question 6

Factors increase in calcitonin secretion

Answer 6

• increase in plasma calcium
• oestrogen, prolactin, dopamine, and beta adrenogenic agonists
• gastrin hormone and CCK (to prevent post-prandial hypercalcemia)

Question 7

Factors inhibiting calcitonin secretion

Answer 7

Decrease in plasma calcium levels

Question 8

Define Tetany

Answer 8

It’s the increased neuromuscular excitability caused by a slight decrease in the plasma calcium

Question 9

mechanism of tetany

Answer 9

1. Due to the decreased plasma calcium levels, there’s a decrease in threshold of the voltage gated sodium channels
2. Therefore, slight mechanical or electric stimuli could cause a spontaneous impulse
3. This causes fibrillary twitches, then spasmodic contractions Of innervated muscle

Question 10

Extreme cases of tetany results in

Answer 10

• Laryngeal muscle spasmodic contraction
• respiratory muscles spasmodic contraction

this leads to:
* Cyanosis
* asphyxia
* death

Question 11

Causes of Tetany

Answer 11

Hypoparathyroidism:
* accidental removal of parathyroid during thyroidectomy
* auto immune destruction of parathyroid

Decreased calcium intake

Decreased calcium absorption:
* vitamin D deficiency
* alkalinity of intestinal content
* presence of oxalates

Alkalosis

Phosphate retention in advanced kidney disease:
* causes secondary drop of calcium, if the store of calcium in the bones is low

Question 12

enumerate types of Tetany

Answer 12

• Latent (hidden) Tetany
• Manifest Tetany

Question 13

plasma calcium levels that show Latent tetany

Answer 13

7-9.4 mg/dl

Question 14

When do manifestations of latent Tetany appear?

Answer 14

Not during rest, instead of during exercise, stress or ischemia

Question 15

Innumerate tests provoking latent Tetany

Answer 15

• Chovestek sign
• Trousseau sign
• Erb’s sign

Question 16

describe Chovestek’s sign test

Answer 16

Test: Tapping the area of the face over facial nerve in front of the ear

Normal: only feel tap

Tetany: hyperexcitability facial nerve leading to involuntary flex twitching of the ipsilateral facial muscles

Question 17

describe Trousseau sign test

Answer 17

Test: Occlude the circulation of the arm for a few minutes with the pressure above the systolic blood pressure to cause ischemia

Normal: feeling of ischemic pain

Tetany: hyperexcitable nerves:
* feeling of ischaemic pain
* involuntary carpal spasm (accoucheur hand) –> flexion of metacarpophalangeal, joints and extension of interphalangeal, joints and adduction of the thumb

Question 18

Describe erb’s sign test

Answer 18

Test: galvanic stimulation by electric current over medial side of the forearm

Normal: reflex contraction during make no reflex during current flow and reflex contraction during a break

Tetany: reflex contraction during the whole period of current flow

Question 19

plasma calcium levels causing manifest tetany

Answer 19

less than 7mg/dl

Question 20

When does manifest Tetany occur ?

Answer 20

during rest

Question 21

Manifestations of manifest tetany

Answer 21

• Carpo-pedal spasm
• Laryngeal spasm
• respiratory spasm
• cyanosis
• asphyxia

Question 22

Treatment of tetany

Answer 22

• Slow IV infusion of Calcium gluconate
• Diet rich in Calcium
• diet rich in vitamin D
• Treat cause (renal failure, alkalosis, lack of absorption)