Thyroid Flashcards Preview

Med 1 Endo > Thyroid > Flashcards

Flashcards in Thyroid Deck (113)
Loading flashcards...
1

This organ rising when swallowing. Roughly 4 cm long; each lobe 2cm wide.

Thyroid

2

Active form of thyroid hormone

T3

3

Storage form of thyroid hormone; and lives longer than the active form

T4

4

Majority of T3 and T4 in the body is bound to what two proteins?

Thyroid Binding Globulin and Albumin

5

Ratio of T3 to T4 in the body (T3:T4)

1:40

6

T3 or T4 is more potent?

T3

7

Half life of T3

1 day

8

Half life of T4

1 week

9

What exogenous item is necessary for ideal thyroid function?

Iodine

10

Where do we get iodine?

Diet and fortified salt

11

How much iodine do we intake on average?

500 mcg

12

What's the least amount of iodine we should intake per day?

150 mcg

13

Excess iodine can lead to?

1. Autoimmune thyroid disease
2. Hypothyroidism as a result of autoimmune disease
3. Thyroid nodule development!

14

What hormone(s) from the hypothalamus controls release of thyroid hormone?

TRH (Thyroid Releasing Hormone)

15

What hormone(s) from the pituitary gland (adenohypophysis) controls release of thyroid hormone?

TSH (Thyroid Stimulating Hormone)

16

What hormone(s) from the Thyroid controls release of thyroid hormone?

Thyroxine (T4)
Tri-iodo-thyro-ine (T3)

17

Describe the positive feedback of Thyroid Hormone Secretion.

Tea Time PTL:

TRH from hypothalamus to the PG stimulating release of TSH which goes to the thyroid stimulating the release of TH

18

Describe the negative feedback of Thyroid Hormone Secretion

TH in excess can cause inhibitory affects at the hypothalamus or PG to reduce TRH or TSH secretion, respectively.

19

What happens when you have iodine deficiency?

Goiter

20

How does iodine deficiency lead to Goiter?

Low iodine --> T3/T4 not synthesized
When TH is LOW, TRH secretion is increased by the Hypothalamus, which leads to an increase in TSH by the PG which stimulates Thyroid to create TH. TH accumulates because the precursors to create T3 and T4 are not there, causing an enlargement of the thyroid gland.

21

Primary causes of Hypothyroidism

1. Autoimmune (most common)
2. Iatrogenic (medically induced)
3. Drug induced
4. Congenital

22

Secondary causes of Hypothyroidism

Loss of signaling from PG (aka Central Hypothyroidism)

23

Physical Exam Findings of Hypothyroidism

Dry, brittle hair with hair loss
Edema of face and eye lids
Thick, heavy tongue with slow speech and coarse voice
Decreased perspiration
Bradycardia (slow HR)
Weight gain (decreased metabolism)
Skin is pale, dry, cold and has rough texture
Lethargic, poor memory, slower, expressionless
Menorrhagia (Changes in menstruation; commonly prolonged and heavy)
Cold intolerance
Delayed deep tendon reflexes

24

Why do we see these physical exam findings in hypothyroidism?

Because TH stimulates everything in the body, so where there isn't enough everything SLOWS!

25

What is the effect of T3/T4 on the body?

Increases mitochondria, ATPase activity, and modulates cholesterol metabolism. This leads to increased energy turn over, a rise in O2 consumption, and development of heat. T3 also stimulates action of Epi and Glucagon and GH.

25

What is the effect of T3/T4 on the body?

Increases mitochondria, ATPase activity, and modulates cholesterol metabolism. This leads to increased energy turn over, a rise in O2 consumption, and development of heat. T3 also stimulates action of Epi and Glucagon and GH.

26

Physical Exam Findings for Myxedema

Slow speech
Absence of sweating
Constipation
Peirpheral Edema (Hard pitting edema is unusual but can happen)
Pallor
Hoarseness
Decreases sense of taste and smell
Muscle cramps, aches, and pains
Dyspnea
Weight changes (usually gain, but weight loss isn't rare)
Diminished auditory acuity
Pleural/Pericardial effusions (rare)

27

Physical Exam Findings for Myxedema

Slow speech
Absence of sweating
Constipation
Peirpheral Edema (Hard pitting edema is unusual but can happen)
Pallor
Hoarseness
Decreases sense of taste and smell
Muscle cramps, aches, and pains
Dyspnea
Weight changes (usually gain, but weight loss isn't rare)
Diminished auditory acuity
Pleural effusions (rare)

28

Lab findings for Hypothyroidism

T4 levels LOW
In primary, TSH levels will be HIGH
In secondary, TSH levels will be LOW
Anemia

29

Why is TSH decreased in secondary (central) hypothyroidism?

Because there is an issue at the PG causing an inability to secrete TSH