Thyroid Flashcards
(122 cards)
1
Q
What is the thyroid?
A
A highly vascular butterfly shaped endocrine organ
2
Q
Where does the thyroid sit?
A
Anterior to the trachea
3
Q
How many lobes is the thyroid made up of?
A
2
4
Q
What are the two lobes joined together by?
A
Isthmus
5
Q
What is on the posterior side of the thyroid?
A
4 smaller glands known as the parathyroid glands
6
Q
What is the thyroid attached to?
A
The thyroid cartilage and upper end of trachea
7
Q
What happens to the thyroid on swallowing?
A
It moves
8
Q
What are the two different types of cells that make up the thyroid?
A
Parafollicular C cells and follicular cells
9
Q
What do the follicles encase?
A
The colloid
10
Q
What is the follicle made up of?
A
Follicular cells
11
Q
Where are the parafollicular cells located?
A
Adjacent to follicular cells
12
Q
What do the parafollicular cells lie within?
A
Connective tissue
13
Q
What do follicular cells produce?
A
thyroglobulin
14
Q
What do parafollicular C cells produce?
A
Calcitonin
15
Q
Where is thyroglobulin stored?
A
In the colloid
16
Q
What is taken up by the follicular cells and extruded into the colloid?
A
Iodine
17
Q
What occurs at the colloid resulting in release of thyroglobulin?
A
Pinocytosis
18
Q
How are thyroid hormones produced from thyroglobulin?
A
Thyroglobulin is acted on by lysosomes within follicular cells
19
Q
What are the two hormones produced in the thyroid?
A
T3 (triiodothyronine) and T4 (thyroxine)
20
Q
What does iodine attach to on thyroglobulin?
A
Tryosine residues
21
Q
What is formed when iodine attaches to tyrosine residues?
A
MIT and DIT
22
Q
What are MIT and DIT?
A
Building blocks of thyroid hormones
23
Q
How many MITs and DITs are T3 and T4 made up of?
A
T3 - 2 x MIT
T4 - MIT + DIT
24
Q
What is the majority of secreted hormones?
A
T4
25
What is more biologically active, T3 or T4?
T3
26
How are thyroid hormones in their active state?
Unbound
27
What is T4 converted to by the liver and kidneys?
T3
28
What are the majority of inactive thyroid hormones bound to?
Albumin
29
What are thyroid hormones responsible for maintaining?
Metabolism, growth, reproduction, behaviour and development
30
What do thyroid hormones work in conjunction with when controlling metabolism?
Growth hormone
31
What effect do thyroid hormones have on metabolism?
Increase protein synthesis and increase glucose and fatty acid plasma levels
32
What other functions do thyroid hormones have besides metabolism?
role in thermogenesis, brain development in neonates, CNS activity, maintain bone turnover and gut motility
33
What effect does growth hormone have on fat tissue?
Increases lipolysis - increases plasma fatty acids
34
What effect does growth hormone have on the liver?
Increases gluconeogenesis - increases plasma glucose
35
What effect does growth hormone have on muscle?
Protein synthesis - decreases plasma AAs
36
What is the role of thyroid hormones in the nervous system?
Increase responsiveness to neurotransmitters
37
How do thyroid hormones increase responsiveness to neurotransmitters?
Increase the number of receptors to these transmitters
38
What two hormones regulate thyroid hormones?
TRH and TSH
39
Where is TSH released from?
Anterior pituitary
40
Where is TRH released from?
Hypothalamus
41
What effect does T3 have on the hypothalamus and anterior pituitary?
Negative feedback
42
Where does TRH have an effect?
On anterior pituitary to release TSH
43
Where does TSH have an effect?
On thyroid gland to release T3 and T4
44
What effect does hyperthyroidism have on the heart?
Increased force and rate
45
What cardiac symptoms will a hyperthyroidism patient experience?
Arrhythmias such as AF and tachycardia and palpitations
46
What complications arise from heat intolerance?
Moist, itchy skin
47
What is a temperature symptom in a hyperthyroidism patient?
Heat intolerance
48
What is the key thing about hyperthyroidism symptoms?
Everything is in overdrive
49
What happens to a patient with hyperthyroidisms weight and why?
They will lose weight - BMR increases
50
What symptoms does a hyperthyroidism patient to do with movement?
Tremor and hyperkinesis
51
What behaviour changes does someone with hyperthyroidism have?
Agitation, anxiety, restlessness
52
What sleep changes does someone with hyperthyroidism have?
They may find it difficult to sleep - due to agitation and lots of energy
53
What changes can occur to the menstrual cycle in someone with hyperthyroidism?
Irregular periods (oligomenorrhoea), loss of libido
54
What is the main cause of hyperthyroidism?
Graves disease
55
What is graves disease?
An autoimmune disease
56
Who does graves disease usually affect?
Middle aged women
57
How does graves disease cause hyperthyroidism?
Thyroid gland is stimulated by an autoantibody - not suppressed by high T3 and T4 levels
58
What is TSI?
thyroid stimulation immunoglobulin produced in graves disease which acts in the same way as TSH
59
What are the normal thyroid function levels?
TSH (0.4 - 4)
T3 (9.9 - 22)
fT4 (0.9 - 2.6)
60
What are the typical thyroid function levels in someone with graves disease?
TSH
61
Which thyroid hormone will always be raised in Graves disease?
T4
62
Why is the TSH low in graves disease?
There are high levels of T3 and T4 which have a negative effect on TSH secretion
63
What are the three main complications only seen in graves disease?
Eye disease (eyes bulging), pretibial myxoedema and a goitre
64
When does eye disease appear in graves?
1-2 years after diagnosis
65
Why is there eye bulging in graves disease?
There are receptors within the tissue and muscle surrounding the eyeball which are similar to TSH receptors - stimulated by TSI - leads to retro-orbital swelling due to inflamm response
66
What causes loss of eye function in graves?
Collagen fibres being deposited in the muscle and tissue surrounding the eye
67
What are the eye symptoms in graves?
Difficulty in eye movement, eye bulging, eyes feel gritty, blurred vision, redness of eyes and decreased colour vision
68
When does pretibial myxoedema occur in graves?
1-2 years after diagnosis
69
What is pretibial myxoedema?
Bilateral plaque formation on the anterior surface aspect of the lower legs
70
What does pretibial myxoedema distinctly look like?
Orange peel - non-pitting
71
When is pretibial myxoedema usually present in graves?
When the patient also has eye disease
72
What is a goitre?
Swelling of the thyroid gland producing a neck lump which can be easily seen and palpated
73
What can a goitre cause?
Compression of local structures - difficulty in breathing and swallowing
74
What is a GI symptom in hyperthyroidism?
Diarrhoea
75
What are the important things to note when examining a goitre?
Movement, nodules, size, bruit
76
What other examinations besides a goitre examination should be done in a patient with suspected hyperthyroidism?
Lid-lag, eye movement, lower legs should be examined
77
What is the second most common cause of hyperthyroidism?
Toxic multi nodular goitre
78
What is TMG?
Presence of functioning autonomous nodules that secrete large amounts of thyroid hormones
79
Where is TMG common?
Areas where population is iodine deficient
80
Is a function adenoma or carcinoma more likely?
Adenoma
81
What is de Quervain's thyroiditis?
Hyperthyroidism initially caused by an acute inflamm process, usually viral in origin
82
What other symptoms besides the classic hyperthyroid symptoms are seen in de Quervain's thyroiditis?
Fever, malaise and local tenderness around thyroid gland
83
What will the blood tests show in de Quervain's thyroiditis?
In acute phase - hyperthyroidism
84
What follows acute phase in de Quervain's thyroiditis?
Transient hypothyroidism before patient goes back to euthyroid state
85
What are the symptoms of hypothyroidism?
Opposite to those in hyperthyroidism - weight gain, slow reflexes, cold intolerance, fatigue, lethargy and increased soft tissue of face, hands and feet
86
What are the symptoms of hypothyroidism not opposite to those in hyperthyroidism?
Coarse sparse hair, expressionless face, cool doughy skin, obstructive sleep apnoea
87
What do the thyroid function tests show in hypothyroidism?
TSH - 45
T3 - 0.03
fT4 - 4
88
What can hypothyroidism be separated into?
Primary and secondary causes
89
What are the two kinds of hypothyroidism with primary causes?
Goitrous
| Non-goitrous
90
What are the two kinds of hypothyroidism with secondary causes?
Hypothalamic and pituitary
91
What is the main cause of hypothyroidism?
Iodine deficiency
92
What is Hashimoto's thyroiditis?
Autoimmune disease causing hypothyroidism
93
What do the antibodies attack in Hashimoto's thyroiditis?
Thyroid peroxidase (amongst others) which is an enzyme used in the production of thyroid hormones
94
Besides TPO what else do antibodies attack in Hashimoto's thyroiditis?
Thyroglobulin - leads to destruction of the follicular cells of thyroid
95
How does the thyroid gland feel in Hashimoto's thyroiditis?
Rubbery, may range from feeling soft to hard
96
What can cause widespread deficiency or loss of function of either the hypothalamus or the pituitary gland?
Infiltration, infection or malignancy of the glands
97
What is the most likely diagnosis when theres increased TSH and decreased T4?
Hypothyroidism
98
What is the most likely diagnosis when theres decreased TSH and increased T3/T4?
Hyperthyroidism
99
What is the most likely diagnosis when theres decreased TSH with normal T4 and T3?
Subclinical hyperthyroidism
100
What is the most likely diagnosis when theres increased TSH and normal T4?
Treated hypothyroidism
101
What is the most likely diagnosis when theres decreased TSH and decreased T4 and T4?
Pituitary disease
102
What test is useful for Hashimotos thyroiditis and graves disease?
Anti-thyroid antibodies
103
What test is done if there is a goitre present and pathology is unknown?
Fine needle aspirate
| U/s or thyroid scan
104
What does a U/S scan of a goitre do?
Allows us to determine whether nodule is solid or cyst like
105
What does a radioactive thyroid scan of a goitre do?
Distinguishes function or non-functioning nodules
106
What is the initial therapy of hyperthyroidism?
Medical treatment
107
What does medical treatment of hyperthyroidism involve?
Inhibition of the production of thyroid hormones from within the gland itself
108
What are the drugs used in medical treatment of hyperthyroidism?
Carbimazole and propylthiouracil (PTU)
109
How are the drugs in hyperthyroidism used?
Started at high dose initially and then gradually reduced over 12-18 months
110
What is it important to check over the course of medical treatment of hyperthyroidism?
Circulating hormone levels - patient may become hypothyroid
111
What is the major side effect of carbimazole?
Agranulocytosis
112
When should a patient immediately stop taking carbimazole?
If they develop a dry cough or sore throat
113
Besides medications for treatment of hyperthyroidism what other drugs are given?
Beta blockers - reduce effect of thyroid hormones on heart
114
What surgery is done in hyperthyroidism?
Sub-total thyroidectomy
115
What happens before a sub-total thyroidectomy?
Patient stops anti-thyroid drug treatment two weeks before
116
What is the risk of a sub-total thyroidectomy?
Patient becoming hypothyroid
117
Besides drugs and surgery what is another treatment done in hyperthyroidism?
Radio-iodine therapy
118
What is radio-iodine therapy?
Radioactive iodine 131 is taken orally to destroy cells within the thyroid gland
119
What happens to most patients who undergo radio-iodine therapy?
They become hypothyroid and require thyroid replacement therapy
120
What is the treatment of hypothyroidism?
Replacement therapy of thyroid hormones
121
What drug is given in hypothyroidism?
An analogue of thyroxine - levothyroxine
122
How long will a patient be on levothyroxine?
The rest of their life
