5.3 Thyroid Gland Flashcards Preview

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Flashcards in 5.3 Thyroid Gland Deck (20):
0

Inhibits T3 and T4 secretion

Dopamine and somatostatin

1

T3 and t4 can regulate levels of TRH and TSH via ________ :
A. Positive feed back
B. ultra short loop negative feedback
C. short loop negative feedback
D. Long loop negative feedback

D. Long loop negative feedback

2

Steps of thyroid hormone synthesis occur
A. Colloid
B. lumen
C. Apical membrane
D. Basal membrane

A. Colloid - where most thyroid hormones are STORED
B. lumen - steps of thyroid hormone synthesis occur Correct answer
C. Apical membrane - lines the lumen
D. Basal membrane - separates cytoplasm and capillary network

3

Enumerate steps of thyroid hormones synthesis by TSH in correct order

Iodide trapping - organification - retrieval of stored hormone - proteolysis - secretion of t3 and t4 - deiodination

4

Inhibits iodide trapping

Thiocyanate and perchlorate anions

5

Inhibits organification

Propylthyrouracil - reduce thyroid hormone synthesis so it is used for tx of hyperthyroidism

6

Iodinated thyroglobulin is taken back by
A. Endocytosis
B. Exocytosis

A. Endocytosis - Megalin

7

Majority of T3 and T4 are
A. Bound
B. Unbound (free)

A. Bound

8

Which is considered to be active
A. Bound
B. Unbound (free)

B. Unbound (free)
Which is why for lab measurement, free hormone levels are best appreciated since binding hormone levels may produce falsely high it low results

9

Which is more tightly bound to TBG? T3 or t4

T4.
It has higher affinity for TBG, meaning it is more TIGHTLY BOUND and slowly liberated giving them a LONGER half life and LONGER duration of action compared to T3.

10

Arrange the following as to highest affinity by T3 and T4
TBG, Transthyretin, Albumin

TBG > Albumin > Transthyretin

11

Which is considered as the biologically active form of thyroid hormone? T3 or T4? Why?

T3 is the biologically active form since it has 10x greater affinity to THR (Thyroid Hormone Receptor).

NOTE: T4 has longer half life and longer duration of action since it has greater affinity to TBG (Thyroxine Binding Globulin).

12

Considered as the major secretory product of the thyroid gland?
T3 or t4

T4 is considered as the major secretory product of the thyroid gland. Since it is the RESERVOIR of T3, t4 is eventually converted to T3.

13

All are DIRECT effects of thyroid hormones except
A. Increased ventricular contractility
B. Increased G protein stimulatory/ inhibitory ratio
C. Increased CO2 and heat production
D. None of the above. All are direct effects.

C. Increased CO2 and heat production - INDIRECT EFFECT

14

Synergistic effects of thyroid hormones

Heat production
Cardiac output
Lipolysis
Gluconeogenesis

15

Which of the following CANNOT BE MEASURED
a. Free t3
B. Free t4
C. TRH
D. TSH

C. TRH

16

In primary hypothyroidism, levels of TSH is
A. Low
B. Normal
C. High

In hypothyroidism T3 and T4 are LOW, TSH levels are HIGH.

17

Kind of goiter characterized by normal T3 and T4
A. Toxic
B. Non toxic

A. Toxic - increased thyroid hormones
B. Non toxic - normal thyroid hormones Correct answer

18

To treat hypothyroidism, what should be given
T3 or T4?

T4 should be given to treat hypothyroidism since T4 will be converted to T3.

19

Which statement/s is/are true?
1. All hyperthyroid patients will end up having thyrotoxicosis
2. Not all thyrotoxic patients have hyperthyroidism

BOTH ARE TRUE.