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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
Subclinical hyperthyroidism
Decreased TSH | Normal/variable T4 + T3
26
Central hypothyroidism
Low TSH | Low T4
27
Sick euthyroidism or pituitary disease
Low TSH | Low T4 and low T3
28
Consider changes in TBG, assay interference, amiodarone or pituitary TSH tumour
Variable TSH | Abnormal T4
29
Thyrotoxicosis
Clinical, physiological + biochemical effects that result from exposure to tissues to excess thyroid hormones
30
Thyrotoxicosis associated with hyperthyroidism
Excessive thyroid stimulation | Thyroid nodules
31
Excessive thyroid stimulation
``` Graves Hashitoxicosis Pituitary TSHoma Trophoblastic disease Germ cell tumours (increased hCG --> thyrotrophic activity) Pituitary thyroid hormone resistance ```
32
Thyroid nodules
Autonomous secretion by either toxic solitary nodules or multinodular goitre
33
Thyrotoxicosis NOT associated with hyperthyroidism
Thyroiditis- drug induced (amiodarone), silent De Quervain's (tender goiter exclusively), subacute (post-partum), radiation induced Exogenous thyroid hormones Ectopic thyroid tissue
34
Thyrotoxicosis symptoms
``` Diarrhoea Weight loss Increased appetite Restlessness Sweats Heat intolerance Palpations Tremor Irritability Labile emotions Oligomenorrhoea +/- infertility Loss of libido ```
35
Thyrotoxicosis Signs
``` Fast/irregular pulse Warm moist skin Fine tremor Palmar erythema Thin hair Lid lag Lid retraction Goitre or thyroid nodules Thyroid bruits ```
36
Grave's
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
Grave's Ophthalmopathy
25-50% | Auto-antibody cross- reaction with orbital autoantigens
38
Grave's Op symptoms
``` Eye discomfort Grittiness Increased tear production Photophobia Diplopia Decreased acuity and colour vision ```
39
Grave's Op signs
``` Exophthalmos Proptosis Ophthalmoplegia Afferent pupillary defect- sign of optic nerve compression Conjunctival oedema Corneal ulceration Papilloedema ```
40
Grave's Op RFs
Smoking | Radioiodine therapy
41
Grave's Op Management
Treat underlying cause Mild- artificial tears, elevation of head at night, sunglasses, avoid dust Severe- steroids, surgical decompression
42
Grave's Dermopathy
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
Toxic adenoma
Solitary focal, diffuse hyperplasia of follicular cells | Secrete thyroid hormones
44
Toxic multinodular goitre
Most common cause of thyrotoxicosis in iodine-deficient areas Also seen in elderly patients Nodules secrete excess thyroid hormones
45
Thyroiditis
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
Thyroid cysts
Benign solitary nodule that creates pressure symptoms | May be painful if it bleeds- aspirate or exercise
47
Hyperthyroidism in pregnancy
``` Increase in circulating thyroid hormones May trigger grave's 1st half of pregnancy- aggravated 2nd half- ameliorated Postpartum- recurrence ```
48
Subclinical hyperthyroidism
``` Normal T3 + $ Suppressed TSH Increases risk of AG Endogenous causes- toxic adenoma, multinodular goitre Exogenous causes- levothyroxine ```
49
Thyroid hormone resistance
Mutation in receptor at pituitary gland Rise in T3 and T4 fails to suppress TSH DDHx TSHoma
50
Medical management Thyrotoxicosis
Beta blockers (control of symptoms) Carbimazole Propylthiouracil
51
Carbimazole- two regimes
Titration- 20-40mg/24hr PO for 4 weeks, reduce according to TFTs every 1-2 months Block-replace: give carbimazole + levothyroxine simultaneously
52
Carbimazole side effects
Agranulocytosis
53
Propylthiouracil
1st trimester of pregnancy Thyroid storm Carbimazole CI
54
Radioactive iodine- thyrotoxicosis
Used for MNG, toxic adenoma, carbimazole-relapsed Graces CIs- pregnancy, lactation, Graves ophthalmopathy SEs- hypothyroidism
55
Thyroidectomy- thyrotoxicosis
Indications- suspected malignancy, compressive symptoms | Complications- recurrent laryngeal nerve damage, hypoparathyroidism, local haemorrhage
56
Thyrotoxicosis Complications
``` HF Angina AF Osteoporosis Ophthalmology Gynaecomastia Thyroid storm ```
57
Thyroid Storm
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
Thyroid storm presentation
``` Severe hyperthyroidism Fever Agitation Confusion Coma Tachycardia AF D+V Goitre Thyroid bruit Acute abdomen HF ```
59
Thyroid storm diagnosis
Do TFTs | Don't wait for test results if urgent treatment needed
60
Thyroid storm Treatment Aim
1) Counteract peripheral effects of thyroid hormones 2) Inhibit thyroid hormone synthesis 3) Treat systemic complications
61
Thyroid storm treatment
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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