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Endocrinology > Thyroid > Flashcards

Thyroid Flashcards

1
Q

How is most of t3 and t4 found?

A

Peripherally bound to thyroxine binding protein (TBG)

Free t3 and t4 are better measured of these hormones as TBG varies and increased TBG means more total t3 and t4.

TBG increased by pregnancy, oestrogen therapy and hepatitis

TBG decreased in nephrotic syndrome and malnutrition (protein loss), drugs, chronic liver disease and acromegaly

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2
Q

High TSH and low T4

A

Primary Hypothyroidism

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3
Q

High TSH and normal t4

A

Treated or subclinical primary hypothyroidism

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4
Q

High TSH and high t4

A

TSH secreting tumour or thyroid hormone resistance

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5
Q

Low TSH and high t4 or t3

A

Primary Hyperthyroidism

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6
Q

Low TSH and normal t3 and t4

A

Subclinical hyperthyroidism

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7
Q

Low TSH and low t4

A

Central aka secondary hypothyroidism - hypothalamus or pituitary problem

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8
Q

Low TSH, t3 and t4

A

Sick euthyroid system or pituitary disease

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9
Q

Normal TSH, abnormal t4

A

Consider changes in thyroid- binding protein,

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10
Q

What test can also be raised in autoimmune thyroid disease?

A

Anti-thyroid peroxidase antibodies or antithyroglobulin antibodies may be increased
Eg. Hashimotos, graves

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11
Q

What 2 scans can be done to look at the thyroid?

A
  1. USS can distinguish between cystic and solid nodules
    Cystic usually but not always benign, solid possibly malignant
  2. Isotope scan - few neutral and almost no hot modules are malignant but a cold module can be malignant (20%)
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12
Q

What is the thyroid system?

A

Thryotropin-releasing hormone secretion from hypothalamus stimulates thyroid-stimulating hormone from anterior pituitary.

This causes release of t3 and t4 from the thyroid gland - mostly t4 which is the peripherally converted to the more active T3.

T3 and T4 negativity feedback on TSH production

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13
Q

Which patients should you screen for thyroid disease? X6

A
  • AF patients
  • hyperlipidaemia patients (high cholesterol in hypothyroidism)
  • DM
  • women with type 1DM during 1st trimester of pregnancy or post-delivery have 3x increased risk of postpartum thyroid dysfunction
- patients on amiodarone (thyroid abnormalities hypo and hyper in 14-18% of patients) 
or lithium (causes hypothyroidism - goitre in 40-50% of patients)
  • patients with downs or turners syndrome or Addison’s disease
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14
Q

Symptoms of thyrotoxicosis

A

Diarrhoea, weight loss, increased appetite

Overactive, sweats and heat intolerance

Palpitations and tremor

Irritability and labile emotions

Oligomenorrhoea

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15
Q

Signs of thyrotoxicosis

A

Pulse - fast or irregular

Warm moist skin and thin hair

Fine tremor and palmar erythema

Onycholysis

Lid lag and lid retraction

Thyroid goitre or nodules or bruit

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16
Q

3 signs of Graves’ disease

A

Eye disease (exophalmos and ophthalmoplegia)

Pretibial myxoedema - oedematous swellings above lateral malleoli

Thyroid acropachy - clubbing, painful finger and toe swelling and periosteal reaction in limb bones

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17
Q

What blood cell/electrolyte manifestation do you get in hyperthyroidism x4

A

Mild neutropenia
Raised ESR
Calcium raised
LFTs raised

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18
Q

Prevalence of Graves

A

0.5% - 5/1000

2/3 of hyperthyroidism

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19
Q

F:M ratio of Graves

A

F:M = 9:1

Associated with other autoimmune diseases eg. t1dm, addison’s, vitiligo

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20
Q

Typical age of presentation of Graves

A

40-60 years

younger if maternal family history

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21
Q

Cause of Graves disease

A

Autoimmune hyperthyroidism

Circulating IgG autoantibodies binding to and activating g-protein coupled thyrotropin receptors

Causing increased thyroid hormone production and smooth enlargement

The autoantibodies also react with orbital autoantigens - eye disease - cause retro-orbital inflammation and lymphocyte infiltration

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22
Q

Triggers of Graves

A

Stress, infection, childbirth

23
Q

8 other causes of hyperthyroidism

A

1) Toxic multi-nodular goitre
- mostly in elderly and iodine deficient areas - nodules secrete thyroid hormones - surgery for compressive symptoms

2) Toxic adenoma
- solitary nodule producing t3 and t4 - nodule is hot and rest suppressed on isotope scan

3) Ectopic thyroid tissue - either metastatic follicular thyroid cancer or struma ovarii - ovarian teratoma with thyroid tissue

4) Exogenous
- Iodine excess (iodine needed for thyroid hormone synthesis therefore can stimulate increased production especially in subacute)
- Contrast media
- Levothyroxine

5) Subacute de Quervain’s thyroiditis
- self-limiting post viral - high temperature, low uptake on isotope scan - treat with NSAIDs

6) Amiodarone
7) Postpartum
8) TB - rare

24
Q

Immediate treatment of hyperthyroidism

A

Beta-blockers for rapid control of symptoms - AF

25
Q

Treatment of hyperthyroidism with anti-thyroid medication

A

Carbimazole - active form is methimazole
Prevents thyroid peroxidase enzyme from coupling and iodinating tyrosine residues on thyroglobulin
Prevents T3 and T4 production

Side effects = agranulocytosis

Can either give dose and titrate until correct dose

Or can block completely with carbimazole and then replace with thyroxine - less chance of iatrogenic hypothyroidism

26
Q

Treatment of Graves

A

Maintain on carbimazole regimen for 12-18months and then withdraw

50% relapse and therefore need surgery or radioiodine

27
Q

2 other types of non-medical therapy for hyperthyroidism

A

Radioiodine (need to avoid pregnancy for 4 months and contact with pregnant women or small children for 2 weeks)

or thyroidectomy

Both risk hypothyroidism

Surgery also risk hypoparathyroidism and damage to recurrent laryngeal nerve

28
Q

Complications in hyperthryoidism 3 x cardiac and 4x other

A

AF, angina, heart failure

Osteoporosis
Opthalmoplegia
Gynaecomastia

Thyroid storm

29
Q

Prevalence of thyroid eye disease in Graves patients and 3 other factors

A

25-50%

Main risk factor is smoking

Eye disease doesn’t correlate with thyroid disease

Can worsen with radioiodine treatment

30
Q

Symptoms of Graves thyroid eye disease

A

Eye discomfort, grittiness, increased tear production

Photophobia, diplopia, decreased visual acuity

RAPD - may mean optic nerve compression

Compression not related to protrusion - often opposite

31
Q

Signs of Graves eye disease

A

Exophthalmos, proptosis

Conjunctival oedema

Corneal ulceration

Papilloedema

Opthalmoplegia

32
Q

Treatment of bad eye disease

A

High dose steroids - if opthalmoplegia or gross oedema

IV methylprednisolone

33
Q

Another name for hypothyroidism

A

Myxoedema

34
Q

Prevalence of hypothyroidism

A

4/1000 (less than hyper)

35
Q

Male to female ratio of hypothyroidism

A

1:6 …M:F

36
Q

Symptoms of hypothyroidism

A

Tired/sleepy, lethargic, cold disliking

Weight gain, constipation and menorrhagia

Low mood, decreased memory and cognition and dementia

Myalgia, cramps and weakness

Hoarse voice

37
Q

Signs of hypothyroidism

A

BRADYCARDIC

Bradycardic

Reflexes relax slowly

Ataxia - cerebellar

Dry + thin skin/hair

Yawning/drowsy/coma

Cold hands + low temp

Ascites - non-pitting oedema +/- pericardial or pleural effusion

Round puffy face/double chin/obese

Defeated demeanour

Immobile +/- ileus

CCF

also goitre, myopathy and neuropathy

38
Q

What is high in hypothyroidism?

A 
Cholesterol and triglycerides 
Also TSH (T4 low) 
Unless rare secondary in which case both TSH and T4 are low
39
Q

What is the biggest cause worldwide of hypothyroidism?

A

Iodine deficiency

40
Q

Iatrogenic causes of hypothyroidism

A

Post thyroidectomy or RI treatment

Drug-induced - antithyroid drugs, amiodarone, lithium, iodine

41
Q

3 other causes of hypothyroidism

A

1) Primary atrophic hypothyroidism - f:m = 6:1, more common in elderly - diffuse lymphocytic infiltration causes atrophy and fibrosis of the gland - no goitre - can also be end stage of diseases such as hashimotos

2) Hashimotos thyroiditis
- goitre due to lymphocytic and plasma cell infiltration
- commoner in women 60-70
- may be hypothyroid or euthyroid
- rarely an initial period of hyperthyroid - hashitoxicosis - autoantibody titres are very high

3) Subacute thyroiditis
- Temporary hypothyroidism after hyperthyroid phase
- can occur in de quervains and post-partum thyroiditis

42
Q

Associations of hypothyroidism

A 
Autoimmune
Turners and Downs
CF
Primary biliary cirrhosis 
Ovarian hyperstimulation

POEMs syndrome

Dyshormogenesis - genetic defect in hormone synthesis

43
Q

Treatment of hypothyroidism in healthy and young

A

Levothyroxine (T4)
50-100ug/24hr
Review at 6 weeks

44
Q

Treatment of hypothyroidism in elderly or IHD

A

Start with 25ug of levothyroxine and titrate up according to TSH levels

Caution because levothyroxine can precipiate angina or MI

45
Q

Amiodarone features

A

It is an anti-arrhythmic drug which is structurally like T4 and is iodine rich
2% of patients get thyroid problems using it
Can be hypo or hyper
Has 80 day half life therefore symptoms persist post-withdrawal

46
Q

What is myxoedema coma?

A

Severe hypothyroidism usually seen in elderly
Hypothermia, hypoventilation, hyponatraemia, heart failure, confusion and coma
Treat with IV T3/T4 + IV hydrocortisone in case due to hypopituitarism

47
Q

What may be low in serum in hypothyroidism

A

Sodium

48
Q

Treatment of acute hyperthyroidism crisis

A

Propylthiouracil, propanolol, IV hydrocortisone (inhibits peripheral conversion of T4 to T3)
Potassium iodide or lugols iodine
Rehydrate and control temperature

49
Q

F/U needed when changing levothyroxine dose

A

8-12weeks

50
Q

TSH level aim when treating hypothyroidism

A

0.5-2.5

51
Q

Management of hypothyroidism in pregnancy

A

Increase dose by 25-50micrograms because increased demand in pregnancy

52
Q

Side effects of levothyroxine therapy

A

Worsening angina
Decreased Bone mineral density
Hyperthyroidism
AF

53
Q

Which syndromes/diseases are associated with thyroid disease and what kind

A

Hypothyroid - downs, turners and addissons disease

Endocrinology (8 decks)

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