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Endo > Thyroid > Flashcards

Thyroid Flashcards

1
Q

Thyroid hormones pathway

A

TRH from hypothalamus stimulates anterior pituitary
Anterior pituitary produces TSH
TSH stimulates T3 and T4 (5x less active), majority produced is T4 as 85% of T3 production is from peripheral T4 conversion
Majority of T4 and T3 bound to thyroxine-binding globulin
Unbound T3 + T4 are active forms, inc cell metabolism + catecholamine effects via nuclear receptors

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2
Q

Factors increasing TBG (and therefore total T3+T4)

A

Pregnancy
Oestrogen therapy (HRT, oral contraceptives)
Hepatitis

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3
Q

Factors decreasing TBG

A 
Nephrotic syndrome
Malnutrition
Drugs (Androgens, corticosteroids, phenytoin)
Chronic liver disease
Acromegaly
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4
Q

Hyperthyroidism test results

A

Increased T4, only ~1% have increased T3

Decreased TSH, unless rare TSH-secreting pituitary adenoma

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5
Q

Hypothyroidism test results

A

Ask only for T4 and TSH, T3 adds nothing

TSH varies through day, trough at 2pm and 30% higher during darkness so test at same time

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6
Q

TFTs in systemic disease

A

Euthyroid but everything low

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7
Q

What is assay interference in TFTs

A

Abs in serum interfering with test

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8
Q

What is thyroid autoantibody test

A

Anti-thyroid peroxidase (TPO) increased in Hashimoto’s/ Graves

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9
Q

What TSH receptor antibody test

A

May be increased in Graves, useful in pregnancy

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10
Q

What is serum thyroglobulin test used for

A

Monitoring treatment of carcinoma

Detection of self-medicated hyperthyroidism where it is low

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11
Q

What is thyroid US used for

A

Distinguishing cystic from solid nodules

If solitary/dominant large nodule in multinodal goitre, do fine-needle aspiration looking for thyroid cancer

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12
Q

Thyroid isotope scan use

A

123-Iodine often used
Useful for determining hyperthyroidism cause + detect retrosternal goitre/ ectopic thyroid tissue/ thyroid metastases (+ whole body CT)
If increased or neutral isotope uptake, unlikely to be malignant, if decreased then 20% chance of malignancy

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13
Q

Thyroid tissue surgery indications

A 
Rapid growth
Compression signs
Dominant nodule on scintigraphy
Nodule ≥3cm
Hypo-echogenicity
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14
Q

Which pt to screen for thyroid abnormalities

A

AF
Hyperlipidaemia

DM (yearly)
Pts with Down’s, Turner’s or Addison’s (yearly)

Women with T1DM during 1st trimester and post delivery

Pts on amiodarone/ lithium 6mthly

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15
Q

What is thyrotoxicosis

A

Clinical effect of excess thyroid hormone

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16
Q

Thyrotoxicosis presentation

A

Diarrhoea, weight loss (if very high paradoxical gain in 10%), appetite inc
Over-active, sweats, heat intolerance
Palpitations, tremor, irritability
Fast pulse, moist warm skin

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17
Q

Thyrotoxicosis tests

A 
Decreased TSH, inc T4/T3
May be mild normocytic anaemia + mild neutropenia
Raised ESR, Ca and LFT
Check thyroid autoAbs
Isotope scan if cause unclear
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18
Q

Thyrotoxicosis causes

A 
Graves' (2/3 of cases)
Toxic multinodule goitre 
Toxic adenoma (solitary 'hot' nodule producing T3/4)
Ectopic thyroid tissue
Exogenous (iodine excess, levothyroxine excess)
Subacute de Quervain's
Amiodarone, lithium (hypo more common)
Postpartum
TB (rare)
19
Q

Graves’ disease pathology

A

IgG stimulates thyrotropin receptors

20
Q

Toxic multinodule goitre features

A

Seen in elderly/iodine deficient areas
Nodules secrete T3/4
Surgery if dysphagia/ dyspnoea

21
Q

Ectopic thyroid tissue causes

A 
Metastatic follicular thyroid cancer
Struma ovarii (ovarian teratoma with thyroid tissue)
22
Q

What is subacute de Quervain’s thyroiditis

A

Self-limiting post viral with painful goitre

23
Q

Subacute de Quervain’s thyroiditis treatment

A

NSAIDs

24
Q

Thyrotoxicosis drug treatment

A

Beta-blockers (propranolol 40mg/6h) for rapid control
Carbimazole 20-40mg/24h PO for 4wks, reduce according to TFTs every 1-2mths
OR Carbimazole + levothyroxine simultaneously
In Graves maintain for 12-18mths then withdraw, 50% relapse
If relapse then radioiodine or excision

25
Q

Carbimazole SE

A

Agranulocytosis, can lead to dangerous sepsis

Warn pt to stop and get urgent FBC if infection signs

26
Q

Thyrotoxicosis further treatment (drugs ineffective)

A

Radioactive 131-Iodine, most become hypothyroid post treatment, CI in pregnancy/ lactation
Thyroidectomy (usually total), pts become hypo post treatment again, risk of recurrent laryngeal damage + hypoparathyroidism

27
Q

Thyrotoxicosis complications

A

Heart failure
Angina
AF

Osteoporosis
Gynaecomastia

Opthalmology

Thyroid storm

28
Q

Eye problems in Graves

A

Exopthalmos (proptosis)
Eyelids retracted from iris exposing sclera
Diplopia (can be corrected with Fresnel prism in one lens of spectacle)

29
Q

Thyroid eye problem treatment

A

Supportive and underlying cause
If severe, IV methylprednisolone (best) or prednisolone 100mg/day PO, decreasing according to symptoms
Surgical decompression if sight-threatening disease or cosmesis

30
Q

Causes of goitre

A 
Diffuse:
Physiological
Graves
Hashimoto's
Subacute de Quervain's (painful)

Nodular:
Multinodular goitre
Adenoma
Carcinoma

31
Q

Hypothyroidism signs

A 
BRADYCARDIC
Reflexes relax slowly
Ataxia
Dry hair
Yawning
Cold hands
Ascites ± non-pitting oedema
Round puffy face
Defeated demeanour
Immobile ± ileus
CCF
32
Q

Hypothyroidism diagnosis

A

TSH ≥4mU/L (unless rare 2˚ hypothyroidism, then decreased) depending on pt
Decreased T4
Cholesterol + triglyceride increased
Macrocytosis (less common is normocytic anaemia)

33
Q

Causes of 1˚ autoimmune hypothyroidism

A

Primary atrophic hypothyroidism - common, lymphocytic infiltration causes atrophy of thyroid so no goitre
Hashimoto’s - lymphocytic + plasma cell infiltration so goitre, very high Ab titre

34
Q

1˚ non-autoimmune hypothyroidism causes

A

Iodine deficiency
Post-thyroidectomy/ radioiodine treatment
Drug-induced (anti-thyroid drugs, amiodarone, lithium, iodine)
Subacute thyroiditis - temp hypo after hyper phase

35
Q

Hypothyroidism associations

A 
Autoimmune disease (T1DM, Addison's, pernicious anaemia)
Turner's, Down's, CF
Genetic conditions (Pendred's if with deafness)
36
Q

Hypothyroid pregnancy problems

A 
Eclampsia
Anaemia
Prematurity/ dec birth weight
Still birth
Post-partum haemorrhage
37
Q

Hypothyroid treatment

A

In healthy + young: levothyroxine (T4) 0-100mcg/24h PO, check TSH 6wkly until normal then yearly
Elderly/ischaemic heart disease: 25mcg/24h dose then inc 25mcg/4wks as needed
If diagnosis unsure stop T4 and check TSH in 6wks

38
Q

Amiodarone thyroid problems

A

Can cause hypo as is iodine rich, iodine excess inhibits T4 release
Can cause thyrotoxicosis from a destructive thyroiditis
T1/2 of amiodarone is ~80d so symptoms continue after drug stopped

39
Q

Myxoedema coma

A

Hypothyroid coma before death

40
Q

Thyroid receptor processes influenced

A

Metabolism of substrates, vitamins, minerals
Modulation of all other hormones and target-tissue responses
Stimulation of O2 use and generation of metabolic heat
Protein synthesis + carb/lipid metabolism regulation
Stimulation of co-enzyme + related vitamin demand

41
Q

Subclinical hypothyroidism clinical features

A

TSH>4mU/L with normal T4 and T3

No symptoms

42
Q

Subclinical hypothyroidism management

A

Confirm raised TSH is persistent in 2-4mths
Recheck history and discuss treatment if non-specific effects affecting pt life
Treat if TSH≥10; +ve thyroid autoAbs; past Graves’; other organ-specific autoimmunity

43
Q

Subclinical hyperthyroidism clinical features

A

Low TSH, normal T3 + T4

41% increase in relative mortality from all causes vs euthyroid

44
Q

Subclinical hyperthyroidism management

A

Confirm suppressed TSH is persistent
Check for non-thyroid cause (pregnancy, pituitary/ hypothalamic insufficiency, TSH-suppressing medication (thyroxine, steroids))
If no symptoms, recheck 6mthly
Carbimazole or propylthiouracil if symptoms + TSH<0.1

Endo (6 decks)

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