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PM3B: Autumn > Thyroid Systems > Flashcards

Flashcards in Thyroid Systems Deck (24):
1

Explain the hypothalamic regulation of thyroid function?

1. Hypothalamus contains parvocellular neurosecretory cells that release Thyrotropin Releasing Hormones (TRH)

2. Inflow of blood from superior hypophyseal artery carries hormones across to anterior pituritary

3. The endocrine then releases to the vein Thyroid Stimulating Hormone- Thyrotropin (TSH)

2

What effect does the thyroid hormones have on basal metabolic rate

Raised O2 consumption

Raised CO2 and heat production

3

What effect does the thyroid hormones have on cardiovascular system

Increases heart rate and force of contraction

4

What effect does the thyroid hormones have on nervous system

Increases activity of sympathetic nervous system

Enhances the sensitivity to catecholamines

5

What effect does the thyroid hormones have on growth and maturation

Embryo development

CNS development

Linear growth (promotes growth hormone effect)

6

What role does C cells play in thyroid follices

Make calcitonin, lowers calcium levels by inhibiting bone breakdown- involved in managing calcium balance

7

How do you form the two types of iodinated molecules?

Combination of Thyroglobulin (contains high amount of tyrosine) with Iodine (I2) made form iodide (I-) taken up from the blood

8

What are the two couple of iodinated molecules called

MIT: mono-iodotyrosine- one iodine per tyrosine

DIT: di-iodotyrosine- two iodines per tyrosine

9

How do you produce Thyroxine (T4)

DIT (di-iodotyrosine) + DIT

10

How do you produce Triiodothyronine (T3)

MIT (mono-iodotyrosine) + MIT

11

Explain how the Thyroid hormones are released

1. Follicular cells take up portion of colloid in lumen (endocytosis)

2. Lysosomal enzymes in follicular cell break down the iodinated thyroglobulin, this creates T3 and T4

3. T3 and T4 diffuse via the plasma membrane of the follicular cell into the blood

12

What is the role of TBG (thyroxine binding globulin)

Releases bound T3 and T4 to exert its biological effect

Needed to circulate blood stream as we know T3 and T4 have poor solubility in water

13

Which is more active between T3 and T4, explain

T3 is more active as it binds to the thyroid hormone with a higher affinity than T4

Local tissues convert T4 into T3 via removal of one iodine

14

Explain how thyroid hormones are transported around the body to have its targeted effect

1. They are lipophilic in nature and are transported in blood stream bound to carrier protein (TBG and albumin)

2. The activated receptor hormone complex can alter the gene expression

3. Newly formed mRNA directs specific synthesis of specific proteins on ribosomes which bind to intracellular receptors on target cell

15

What are the three diseases associated with the thyroid hormone

Goitre

Cretinism

Grave's disease

16

Describe what goitre is

Hypertrophy of thyroid gland (too much TSH stimulation)

Associated with hypo/hyperthyroidism forms

Association with autoimmune disease

17

What can hypothyroidism lead to symptom wise

Weight gain
Cold intolerance
Lethargy and depression
Puffiness of skin and muscles
Muscular weakness
Sluggish Reflexes
Reduced pulse and cardiac output

18

Describe what cretinism is

Hypothyroidism in kid that can cause fetal brain damage
Shortness
Obesity
Mental retardation

19

How do you treat hypothyroidism

Life long replacement with T4

Levothyroxine- identical to natural T4

20

What is the drug that is identical to T3 and T4 called

Liothyroxine- T3

Levothyroxine- T4

21

What is Hashimoto's thyroiditis

An autoimmune disease that causes damage to the gland which can lead to hypothyroidism

22

What are the symptoms of hyperthyroidism

Weight loss
Nervousness
High cardiac output
Heat intolerance
Hand tremor
eyeball protrusions

23

What is Grave's disease

Cause of hyperthyroidism
Peculiar form of autoimmune disease
Reason: Thyroid stimulating antibody that mimics TSH
HIGH T3/T4, LOW TSH, goitre

24

How do you treat hyperthyroidism

Interfere with thyroid synthesis by blocking the thyroid peroxidase enzyme (prevents iodination of thyroglobulin)

Drug: CARBIMAZOLE