Thyroid

Question 1

Which gland is most important for basal metabolic regulation?

Answer 1

Thyroid gland

Question 2

What is the isthmus?

Answer 2

Connecting tissue between the lobes of the thyroid. Hard to find in dogs and cats

Question 3

What is the effect of thyroid hormone on oxygen?

Answer 3

Increase consumption of oxygen in target cells

Question 4

What are some functions of thyroid hormone?

Answer 4

• Maintain function of organs
• Consumption of )2
• Lipid and carb metabolism
• Normal growth and maturation
• Regulation of calcium

Question 5

What is the location of the thyroid gland?

Answer 5

Bilateral around trachea. Carotid sheath is lateral. Medial retropharyngeal is cranial. Deep to sternothyroideus muscle. and larynx is cranial

Question 6

Where is the parathyroid gland?

Answer 6

Usually 4 and embedded in and is not normally palpable

Question 7

What are follicular cells?

Answer 7

• Traps iodide and transport
• Synthesize and secrete thyroglobulin
• Remove and secrete T3 and T4

Question 8

What are parafollicular cells?

Answer 8

In the thyroid.

• secrete calcitonin
• neural crest derivative
• decrease calcium levels

Question 9

What is in follicles of the thyroid?

Answer 9

Colloid

Question 10

What organ has the greatest blood flow per gram of tissue?

Answer 10

Thyroid

Question 11

Which cells in the thyroid are pituitary independent?

Answer 11

Parafollicular cells

Question 12

Were is iodine found in the body?

Answer 12

In the intestinal tract from feed and are trapped by follicular cells and through active transport enter the follicle

Question 13

What happens to iodine when it enters the follicle?

Answer 13

Attached to Tyrosine by thyroperoxidase and makes either MIT (1 iodine) or DIT(2 iodines)

Question 14

What is thyroglobulin?

Answer 14

In the colloid with many tyrosine residues and gets released to form T3 and T4

Question 15

What is the ultimate effect of T3?

Answer 15

Increase basal metabolism

Question 16

How do you get T3?

Answer 16

1 MIT + 1 DIT + thyroglobulin

Question 17

Where does formation of MIT and DIT happen?

Answer 17

in the lumen???

Question 18

How do you get T4?

Answer 18

DIT +DIT + thyroglobulin

Question 19

What is reverse T3?

Answer 19

Order of addition of tyrosine is opposite. 3, 3’, 5’ tyrosines

Question 20

Which thyroid hormone exists in the most amount?

Answer 20

T4

Question 21

Where are receptors for thyroid hormone?

Answer 21

In the nucleus

Question 22

How is thyroid hormone liberated from thyroglobulin?

Answer 22

1. Endocytosis by thyroid epithelial cells
2. Lysosomes fuse with endocytotic vesicles
3. Free thyroid hormones diffuse from lysosomes into the blood.

Question 23

What can transport thyroid hormones

Answer 23

1. Thyroxine binding globulin (TBG) (70%)
2. Transthyretin (10-15%)
3. Albumin (20%)

Question 24

What animals do not have TGB?

Answer 24

Rodents and cats

Question 25

What cells produce calcitonin?

Answer 25

Thyroid parafollicular cells

Question 26

What does calcitonin do?

Answer 26

Lower blood Ca and phosphorus - Blocks osteoclasts action so it is stored in bones - BLocks renal reabsorption of Ca and P

Question 27

What it the antagonistic hormone to parathyroid hormone?

Answer 27

Calcitonin

Question 28

What 3 hormones regulate calcium?

Answer 28

- Calcitonin (lower) - Vitamin D (raise) - Parathyroid hormone (raise)

Question 29

What is a goiter?

Answer 29

Gross enlargement of the thyroid usually nonneoplastic and non-inflammatory

Question 30

What animal is hyperthyroidism most common in?

Answer 30

Cats. Very rare in dog

Question 31

How many months worth of thyroid hormone is stored in the thyroid?

Answer 31

6months

Question 32

What is a primary hyperthyroidism?

Answer 32

Thyroid adenoma or enlargement

Question 33

What is a secondary cause of hyperthyroidism?

Answer 33

Pituitary tumors or adenoma

Question 34

What is a tertiary cause of hyperthyroidism?

Answer 34

Hypothalamic legion

Question 35

What are some clinical signs of hyperthyroidism?

Answer 35

- increased metabolic rate (heat intolerance) - Goiter - Weight loss, polyphagia, PU - Hyperactivity - Tachycardia - Cardiac murmur - Diarrhea - Serum enzymes elevated - Low plasma cholesterol - Bulging eyes in humans (sympathetic drive)

Question 36

How can you diagnose hyperthyroidism?

Answer 36

- Serum T4 - TSH stimulation test - Thyroid scan - Needle biopsy

Question 37

What is the treatment of hyperthyroidism?

Answer 37

- Antithyroid drugs (inhibit thyroperoxidase) - Radioactive iodine - Surgery - Propanolol for tachycardia

Question 38

What is hypothyroidism?

Answer 38

Deficiency of thyroid follicular hormones

Question 39

What is cretinism?

Answer 39

Irreversible growth and metabolic retardation due to lack of thyroid hormones

Question 40

Why is it important to catch hypothyroidism in young animals?

Answer 40

Without treatment there can be permanent growth damage and retardation

Question 41

What are the signs of hypothyroidism?

Answer 41

- Elevated thyroglobulin antibodies - Poor response to TSH - High serum cholesterol - Alopecia - Lethargy - Cold intolerance - Obesity - Bradycardia

Question 42

What is treatment for hypothyroidism?

Answer 42

Thyroid replacement therapy