(28-2) thyroid/parathyroid

Question 1

(Thyroid/Parathyroid)

1. most common endocrinopathy in what?

Answer 1

1. dogs and older cats

Question 2

(Thryoid hormones)

1. thryoid hormones affect fundamental physiologic processes - what three?

Answer 2

1. cellular differentiaton
2. growth
3. metabolism

Question 3

(Thyroid hormones)

1-2. What are the two active thyroid hormones?

3. differ how?

Answer 3

1. T3 (triiodothyroinine) - more active
2. thyroxine - T4 (higher levels secreted)
3. by one binding to iodide

(one inactive hormone - reverse triiodothryonine)

Question 4

(Thyroid Chemistry)

1. solubility in water?
2. how are T3 an T4 in blood?
3. What is the main carrier?
4. What do carrier proteins allow for?

Answer 4

1. poorly soluble
2. 99% bound to carrier proteins
3. thryoxine-binding globulin
4. maintenance of a stable pool of thyroid hormones (from which the active, free hormones are released for by uptake of target cells)

Question 5

1. T3 is secreted - but most results from what?

Answer 5

1. most results from T4 deiodination in peripheral tissues (liver, kidney)

Question 6

1. follicular epithelail cells secrete what?
2. Parafollicular cells (C cells) secrete what?

Answer 6

1. T3 and T4
2. calcitonin

Question 7

(Parathyroid gland structure)

1. cells that secrete PTH are arranged how?

Answer 7

1. in dense cords around abundant capillaries

Question 8

(Synthesis and Secretion of Thyroid Hormone)

just read this - you already know it in more detail

Question 9

(look at these slides)

its review

Answer 9

(and this)

Question 10

and this

Answer 10

and this

Question 11

(Releasing the thyroid hormones)

1. epithelial cells ignest colloid by what?

2.

fucki ti - just read this too

Answer 11

1. endocytosis

Question 12

(All processes stimulated by TSH)

1-4. Binding of TSH to receptor on epithelial cells stimulates sytnehsis of what 4 things?

Answer 12

1. iodine transporter
2. thryoid peroxidase
3. thyroglobulin
4. magnitude of TSH signal also sets the rate of colloi endocytosis

Question 13

(Physiological Effect of Thyroid Hormones)

1. Target cels?
2. affect what three things?

(Metabolism)

3. basal metabolic rate?
4. heat production? (due to what)?

Answer 13

1. all body cells probably
2. development, growth, and metabolism
3. increases
4. increased (increased O2 consumption and ATP hydrolysis)

Question 14

(Binding of Thryoid hormones in circulation)

1. circulate how?
2. three binding proteins?
3. how much is bound?
4. What is active?

Answer 14

1. bound or free
2. thyroxine-binding globulin (TBG - main one), prealbumin, albumin
3. >90%
4. free hormone

Question 15

(Binding of thryoid hormones in circulation)

1. Changes in binding proteins will influence what?
2. Hepatic failure: TBG decrease due to decreased synthesis in liver. Decrease in TBG causes a transient increase or decrease in free hormone?

Answer 15

1. thyroid concentrations
2. increase (more readily available active form)

Question 16

(Binding of Thyroid Hormones in Circulation)

1. Whenare reduced binding proteins suspected?
2. TBG defects can be cause by nephrotic syndrome, chronic renal failure, liver disease. Sever systemic illness, Cushings, drugs
3. Does TBG deficiency cause hyperthyroidism?

Answer 16

1. abnormally low TT4 (total T4) encountered in normal thryoid animal (normal TSH)
3. no (total T4 and T3 may be low - bute free T4 T3 and TSH all normal)

Question 17

look at this (and probably learn it - but maybe not)

Question 18

look at this

Answer 18

and this