Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MEH (Milly's) > Thyroid > Flashcards

Thyroid Flashcards

1
Q

Where is the thyroid gland?

A

Lies against and around front larynx and trachea

Below thyroid cartilage (adams apple)

Isthmus (middle bit) extends from 2nd to 3rd rings of trachea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the shape of the thyroid?

A

2 lobes joined by isthmus

‘Bow tie’ shape and location

Parathyroid glands side on the posterior side of the lobes (2 on each lobe).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the histology of thyroid tissue?

A

Colloid sits within a follicle

A follicle is a sphere made from follicular cells

*colloid is “extracellular” even though it is inside the follicle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the cells called that are found within the parathyroid gland?

A

Principal/chief cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do the chief cells of the parathyroid gland produce?

A

Parathyroid hormone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the two types of cells found in the thyroid gland?

A

Follicular

Parafollicular

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What do follicular cell within the thyroid gland produce?

A

Thyroid hormone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What do parafollicular cells within the thyroid gland produce?

A

Calcitonin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the substrates that make T3 thyroid hormone?

A 
Monoiodotyrosine
\+
Diiodotyrosine 
=
Triiodothyronine

*1 iodine plus 2 iodine equals 3 iodines hence the tri-iodo bit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the substrates that make the T4 thyroid hormone?

A 
Diiodotyrosine
\+
Diiodotyrosine 
=
Tetraiodothyronine (thyroxine)

*2 iodines+ 2 iodines= 4 iodines hence the tetra-iodo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the proper names of thyroid hormones T3 and T4?

A

T3: triiodothyronine

T4: tetraiodothyronine (thyroxine)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How are thyroid hormones made and stored within the thyroid?

A
  1. Many tyrosine residues are attached to the thyroglobulin proteins (sitting in the colloids)
  2. These residues are iodinated
  3. Different residues couple up forming T3/T4 hormones
  4. They are still attached to the thyroglobulin protein at this point though, but can be easily released if needs be
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What enzyme is responsible for regulating thyroid hormone synthesis?

A

Thyroid peroxidase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What 3 reactions (involving iodine) thyroid peroxidase regulate/

A
  1. Oxidation iodide to iodine (requires presence of H2O2)
  2. addition of iodine to tyrosine acceptor residues on the protein thyroglobulin
  3. Coupling of MIT/DIT to generate thyroid hormones within the thyroglobulin protein
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is dietary iodine taken into the thyroid?

A

Iodide is taken up from the thyroid epithelial cells, which have a sodium-iodide symporter.

*iodine is reduced to iodide before absorption principally in the small intestine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How are thyroid hormones released?

A

Thyroglobulin is brought into the thyroid follicular cell by pinocytosis

It is engulfed by a lysosome which breaks down the thyroglobulin, freeing the thyroid hormones which can then be released into the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How is T3 and T4 transported around the body?

A

In the blood, bound to proteins called thyroxine-binding globulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Which of the thyroid hormones makes up the largest proportion of hormones released by the gland? What happens to this hormone and why?

A

T4-thyroxine

It is converted to T3 (mostly in liver and kidneys) because T3 (triiodothyronine) is more biologically active

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

List the steps, starting with the hypothalamus, that lead to the production of thyroid hormones

A
  1. Hypothalamus releases TRH (thyrotropin releasing hormone)
  2. This stimulates the anterior pituitary gland which releases thyroid stimulating hormone (TSH)
  3. This stimulates the thyroid gland which releases thyroid hormones
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What protein group does thyroid stimulating hormone (TSH) belong to and where is it released from?

A

Glycoprotein, released from the anterior pituitary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the structure of TSH/ thyroid stimulating hormone?

A

Glycoprotein hormone composed of 2 non-covalently bound subunits (alpha and beta)

  • alpha submit is also present in FSH and LH
  • *Beta subunit provides unique biological activity
22
Q

What type of receptor does TSH/thyroid stimulating hormone act upon?

A

GPCR
(Gs)

(Gq pathway also activated at higher TSH concentrations)

*range of signalling pathways

23
Q

What sort of of things does TSH/thyroid stimulating hormone stimulate?

A
  1. Iodide uptake
  2. Iodide oxidation
  3. Thyroglobulin synthesis
  4. Thyroglobulin iodisation
  5. Colloid pinocytosis into cell
  6. Proteolysis of thyroglobulin
  7. Cell metabolism and growth
24
Q

What are the general actions of thyroid hormone?

A
  1. Increase in basal metabolic rate and basal production
  2. stimulation of metabolic pathways
  3. Sympathomimetic effects
25
Q

How do thyroid hormones stimulate metabolic rate?

A
  1. Increase the number and size of mitochondria

2. Stimulate the synthesis of enzymes in the respiratory chain

26
Q

What metabolic pathways are stimulated by the thyroid hormones?

A

Catabolic are generally stimulated more than anabolic:

  1. Lipid metabolism
  2. Carbohydrate metabolism
27
Q

What effect do thyroid hormones have on lipid metabolism?

A

Stimulate lipolysis and beta oxidation of fatty acids

28
Q

What effect do thyroid hormones have on carbohydrate metabolism?

A

Stimulate insulin-dependent entry of glucose into cells and increase gluconeogenesis and glycogenolysis

29
Q

What sympathomimetics effects do thyroid hormones have on the body?

A

Increases target cell response to catecholamines by increasing receptor number on target cells

30
Q

What effect do thyroid hormone have on the cardiovascular system?

A

Increase hearts responsiveness to catecholamines:

  1. This increases CO (due to increased HR and iontropy)
  2. This also increases the peripheral vasodilation to carry extra heat to body surface
31
Q

What effect do thyroid hormones have on the nervous system?

A

Essential for both development and adult function

The hormones increase myelination of nerves and development of neurones

32
Q

What type of receptors do thyroid hormones work on?

A

Nuclear receptors

33
Q

How do nuclear receptors carry out responses?

A

Act by relieving the suppressing of gene expression

Thyroid hormone receptors bind DNA in the absence of hormone

Hormone binding is associated with a conformation change in the receptor that causes it to function as a transcriptional activator

34
Q

Thyroid hormone receptors are pre-bond to specific DNA sequences on DNA, what are these called?

A

Hormone response elements (HRE)

*in the promoter region of thyroid hormone regulated genes

**expression of new protein mediates the effected of thyroid hormone

35
Q

Give some examples of thyroid hormone activated genes

A

PEPCK
Ca2+ ATPase
Na+,K+ATPase
Cytochrome oxidase

36
Q

What is goitre?

A

Enlargement of thyroid gland

  • *may accompany either hypo/hyperthyroidism
  • develops when the thyroid gland is overstimulated
37
Q

What is hypothyroidism?

A

Insufficient secretion of thyroid hormones

38
Q

What are the causes of hypothyroidism?

A
  1. Failure of thyroid gland
  2. TSH or TRH deficiency
  3. Inadequate dietary supply of iodine
  4. Radioactive iodine
  5. Autoimmunity
  6. Post surgery (removal of thyroid)
  7. Congenital
  8. Anti-thyroid drugs
39
Q

What are the general symptoms of hypothyroidism?

A 
Obesity
Lethargy
Intolerance to cold
Bradycardia
Dry skin 
Alopecia (hair loss- outer bit of eyebrow)
Hoarse voice 
Constipation
Slow reflexes 
Low T3
LowT4
Elevated TSH
Menorrhagia (heavy periods)
40
Q

If hypothyroidism occurs in infants what happens?what does this mean?

A

Cretinism:

  1. Dwarfed stature
  2. Mental deficiency
  3. Poor bone development
  4. Slow pulse
  5. Muscle weakness
  6. GI disturbances
41
Q

If hypothyroidism occurs in adults, what can occur and what is a result of this?

A

Myxedema:

  1. Thick puffy skin
  2. Muscle weakness
  3. Slow speech
  4. Mental deterioration
  5. Intolerance to cold
42
Q

What is the most common cause of hypothyroidism?

A

Hashimoto’s disease

43
Q

What is hashimoto’s disease?

A

Autoimmune disease resulting in the destruction of thyroid follicles- hypothyroidism

  • women more likely to get it
  • *goitre may or may not be present
44
Q

What is the treatment?

A
  • Oral thyroid hormone

- T4 used since longer half-life

45
Q

What is hyperthyroidism?

A

Over stimulation of the thyroid, too much thyroid hormone

46
Q

What are the causes of the hyperthyroidism?

A
  1. Autoimmune graves’ disease
  2. Toxic multi-nodular goitre
  3. Solitary toxic adenoma
  4. Excessive T4 (or T3) therapy
  5. Drugs- amiodarone
  6. Thyroid carcinoma
  7. Ectopic thyroid tissue
47
Q

What are the general symptoms of hyperthyroidism?

A
  1. Weight loss
  2. Irritability
  3. Heat intolerance, sweating warm vasodilated hands
  4. Tachycardia
  5. Fatigue, weakness
  6. Increased bowel movements- increased appetite
  7. Possible tremor of outstretched hands
  8. Hyper-reflexive
  9. Breathlessness
  10. Loss of libido
  11. Sweating and tremor
  12. Goitre (in some)
  13. Bulging eyes (in some)
48
Q

What is graves’ diseases?

A
  • Autoimmune disease resulting in hyperthyroidism
  • caused by production of thyroid stimulating immunoglobulin (TSI) which continuously stimulate thyroid hormone secretion outside normal negative feedback control!

Causes exophthalmos and pretibial myxoedema

49
Q

What are the symptoms of Graves’ disease?

A
  1. Increased BMR
  2. Excessive sweating
  3. Decrease in body weight
  4. Muscle weakness
  5. Heart palpitations
  6. Bulging eyes (not alway)
  7. Increased T3
  8. Increased T4
  9. V low TSH
50
Q

Name a drug that can be used to treat hyperthyroidism eg Graves’ disease. How does it work?

A

Carbimazole (pro-drug)
Converted to methimazole in the body

This prevents thyroid peroxidase from coupling and iodinating tyrosine on thyroglobulin

**have a store of thyroid hormone so this drug will take effect over a couple of weeks

MEH (Milly's) (39 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions