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Met 3b > Thyroid > Flashcards

Thyroid Flashcards

1
Q

Blood supply to thyroid

A

Branches of superior cerebellar artery + common carotid into the superior and inferior thyroid arteries

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2
Q

Thyroid drainage

A

Superior + middle thyroid veins –> IJV

Inferior thyroid vein –> brachiocephalic vein

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3
Q

Follicular cells

A

Produce T3 and T4

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4
Q

Parafollicular cells

A

Produce calcitonin

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5
Q

Circulating thyroid hormones

A

T3 and T4 bound by TBG

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6
Q

Increased TBG conditions

A

Pregnancy

–> oestrogen inhibits hepatic breakdown

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7
Q

Decreased TBG conditions

A

liver failure

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8
Q

Increased TBG

A

More T3/4 will be bound, less T3/4 will be free

In pregnancy, even though increased TBG, normal free T3/4 as the T3/4 is also increased

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9
Q

Thyroid hormone potency

A

T3 more potent

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10
Q

T4–>T3

A

Increased in obesity

Decreased in pregnancy, fasting, stress, hepatic failure, renal failure, beta blockers

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11
Q

Thyroid hormone control

A

Hypothalamus –> TRH –> Pituitary –> TSH –> Thyroid –> T3+T4

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12
Q

TSH effect

A

Increases T4/3
Hypertrophy and hyperplasia of thyroid follicular cells
Increased blood flow to thyroid

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13
Q

T3/4 on BMR

A

Increased Na/K ATPase activity to increase O2 production and heat

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14
Q

T3/4 on Metabolism

A 
Increased glucose uptake and absorption
Increased glycogenolysis
Increased gluconeogenesis
Increased insulin
Increased FA oxidation
Decreased cholesterol in plasma
Decreased muscle mass
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15
Q

T3/4 on Cardiorespiratory

A

Increased HR and CO
Increased vasodilation
Increased ventilation

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16
Q

T3/4 on CNS

A

Increased SNS activity

Affects mental state- hyper, anxious, nervous

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17
Q

T3/4 on skeletal

A

Increases growth plate chondrocytes + osteoblasts

Increased osteoclast activity (in thyrotoxicosis –> osteoporosis)

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18
Q

T3/4 on reproductive

A

Thickens endometrium in females

Hypothyroidism associated with infertility

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19
Q

T3/4 on development

A

Potentiates growth

Potentiates foetal and neonatal brain development

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20
Q

Hypothyroidism

A

Increased TSH

Decreased T4

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21
Q

Treated hypothyroidism or subclinical hypothyroidism

A

Increased TSH

Normal/variable T4

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22
Q

TSH secreting tumour or thyroid hormone resistance

A

Increased TSH

Increased T4

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23
Q

Slow conversion T4–>T3 or thyroid hormone antibody artefact

A

Low TSH
High T4
Low T3

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24
Q

Hyperthyroidism

A

Low TSH

Increased T4 or T3

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25
Q

Subclinical hyperthyroidism

A

Decreased TSH

Normal/variable T4 + T3

26
Q

Central hypothyroidism

A

Low TSH

Low T4

27
Q

Sick euthyroidism or pituitary disease

A

Low TSH

Low T4 and low T3

28
Q

Consider changes in TBG, assay interference, amiodarone or pituitary TSH tumour

A

Variable TSH

Abnormal T4

29
Q

Thyrotoxicosis

A

Clinical, physiological + biochemical effects that result from exposure to tissues to excess thyroid hormones

30
Q

Thyrotoxicosis associated with hyperthyroidism

A

Excessive thyroid stimulation

Thyroid nodules

31
Q

Excessive thyroid stimulation

A 
Graves
Hashitoxicosis
Pituitary TSHoma
Trophoblastic disease
Germ cell tumours (increased hCG --> thyrotrophic activity)
Pituitary thyroid hormone resistance
32
Q

Thyroid nodules

A

Autonomous secretion by either toxic solitary nodules or multinodular goitre

33
Q

Thyrotoxicosis NOT associated with hyperthyroidism

A

Thyroiditis- drug induced (amiodarone), silent De Quervain’s (tender goiter exclusively), subacute (post-partum), radiation induced
Exogenous thyroid hormones
Ectopic thyroid tissue

34
Q

Thyrotoxicosis symptoms

A 
Diarrhoea
Weight loss
Increased appetite
Restlessness
Sweats
Heat intolerance
Palpations
Tremor
Irritability
Labile emotions
Oligomenorrhoea +/- infertility
Loss of libido
35
Q

Thyrotoxicosis Signs

A 
Fast/irregular pulse
Warm moist skin
Fine tremor
Palmar erythema
Thin hair
Lid lag
Lid retraction
Goitre or thyroid nodules
Thyroid bruits
36
Q

Grave’s

A

Most common cause of hyperthyroidism
Triggered by stress, infection and childbirth
Women 40-60 (mainly)
IgG antibodies that bind to and activate TSH receptors, causing smooth thyroid enlargement + thyroid hormone production
Associated with other autoimmune- vitiligo, T1DM, Addison’s
Patients often hyperthyroid but may be or become hypo or euthyroid

37
Q

Grave’s Ophthalmopathy

A

25-50%

Auto-antibody cross- reaction with orbital autoantigens

38
Q

Grave’s Op symptoms

A 
Eye discomfort
Grittiness
Increased tear production
Photophobia
Diplopia
Decreased acuity and colour vision
39
Q

Grave’s Op signs

A 
Exophthalmos
Proptosis
Ophthalmoplegia
Afferent pupillary defect- sign of optic nerve compression
Conjunctival oedema
Corneal ulceration 
Papilloedema
40
Q

Grave’s Op RFs

A

Smoking

Radioiodine therapy

41
Q

Grave’s Op Management

A

Treat underlying cause
Mild- artificial tears, elevation of head at night, sunglasses, avoid dust
Severe- steroids, surgical decompression

42
Q

Grave’s Dermopathy

A

Pretibial myxoedema- oedematous swelling above lateral malleoli
Thyroid acropachy- extreme manifestation with clubbing, painful finger and toe swelling, and periosteal reaction in limb bones

43
Q

Toxic adenoma

A

Solitary focal, diffuse hyperplasia of follicular cells

Secrete thyroid hormones

44
Q

Toxic multinodular goitre

A

Most common cause of thyrotoxicosis in iodine-deficient areas
Also seen in elderly patients
Nodules secrete excess thyroid hormones

45
Q

Thyroiditis

A

Hormone synthesis is not increased but there is destruction of thyroid follicular cells, resulting in transient increase in thyroid hormones- once exhausted the patient becomes hypothyroid e.g. Hashimoto

46
Q

Thyroid cysts

A

Benign solitary nodule that creates pressure symptoms

May be painful if it bleeds- aspirate or exercise

47
Q

Hyperthyroidism in pregnancy

A 
Increase in circulating thyroid hormones
May trigger grave's
1st half of pregnancy- aggravated
2nd half- ameliorated
Postpartum- recurrence
48
Q

Subclinical hyperthyroidism

A 
Normal T3 + $
Suppressed TSH
Increases risk of AG
Endogenous causes- toxic adenoma, multinodular goitre
Exogenous causes- levothyroxine
49
Q

Thyroid hormone resistance

A

Mutation in receptor at pituitary gland
Rise in T3 and T4 fails to suppress TSH
DDHx TSHoma

50
Q

Medical management Thyrotoxicosis

A

Beta blockers (control of symptoms)
Carbimazole
Propylthiouracil

51
Q

Carbimazole- two regimes

A

Titration- 20-40mg/24hr PO for 4 weeks, reduce according to TFTs every 1-2 months
Block-replace: give carbimazole + levothyroxine simultaneously

52
Q

Carbimazole side effects

A

Agranulocytosis

53
Q

Propylthiouracil

A

1st trimester of pregnancy
Thyroid storm
Carbimazole CI

54
Q

Radioactive iodine- thyrotoxicosis

A

Used for MNG, toxic adenoma, carbimazole-relapsed Graces
CIs- pregnancy, lactation, Graves ophthalmopathy
SEs- hypothyroidism

55
Q

Thyroidectomy- thyrotoxicosis

A

Indications- suspected malignancy, compressive symptoms

Complications- recurrent laryngeal nerve damage, hypoparathyroidism, local haemorrhage

56
Q

Thyrotoxicosis Complications

A 
HF
Angina
AF
Osteoporosis
Ophthalmology
Gynaecomastia
Thyroid storm
57
Q

Thyroid Storm

A

Life-threatening health condition that is associated with untreated or undertreated hyperthyroidism. During thyroid storm, an individual’s heart rate, blood pressure, and body temperature can soar to dangerously high levels

58
Q

Thyroid storm presentation

A 
Severe hyperthyroidism
Fever
Agitation
Confusion
Coma
Tachycardia
AF
D+V
Goitre
Thyroid bruit
Acute abdomen
HF
59
Q

Thyroid storm diagnosis

A

Do TFTs

Don’t wait for test results if urgent treatment needed

60
Q

Thyroid storm Treatment Aim

A

1) Counteract peripheral effects of thyroid hormones
2) Inhibit thyroid hormone synthesis
3) Treat systemic complications

61
Q

Thyroid storm treatment

A

IV access, fluids, NG tube if vomiting
Take blood for TSH, T3, 4 cultures
Sedate if necessary, monitor BP
Propanolol 60mg/4-6h PO, only if normal CO and no CI
–> if asthma/decreased CO, can cause cardiac arrest
High dose digoxin to slow heart
Anti-thyroid drugs- carbimazole 15-25mg/6h PO + after 4h give Lugol’s (iodine) solution 0.3ml/8h PO to block thyroid
Hydrocortisone 100mg/6h IV or Dexamethasone 15-25mg/6h PO
Treat infection if suspected
Adjust IV fluids

Met 3b (21 decks)

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