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Endocrinology > Thyroid > Flashcards

Thyroid Flashcards

(53 cards)

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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

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A

Stress, infection, childbirth

23
Q

8 other causes of hyperthyroidism

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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

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A

Beta-blockers for rapid control of symptoms - AF

25
Treatment of hyperthyroidism with anti-thyroid medication
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
Treatment of Graves
Maintain on carbimazole regimen for 12-18months and then withdraw 50% relapse and therefore need surgery or radioiodine
27
2 other types of non-medical therapy for hyperthyroidism
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
Complications in hyperthryoidism 3 x cardiac and 4x other
AF, angina, heart failure Osteoporosis Opthalmoplegia Gynaecomastia Thyroid storm
29
Prevalence of thyroid eye disease in Graves patients and 3 other factors
25-50% Main risk factor is smoking Eye disease doesn't correlate with thyroid disease Can worsen with radioiodine treatment
30
Symptoms of Graves thyroid eye disease
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
Signs of Graves eye disease
Exophthalmos, proptosis Conjunctival oedema Corneal ulceration Papilloedema Opthalmoplegia
32
Treatment of bad eye disease
High dose steroids - if opthalmoplegia or gross oedema IV methylprednisolone
33
Another name for hypothyroidism
Myxoedema
34
Prevalence of hypothyroidism
4/1000 (less than hyper)
35
Male to female ratio of hypothyroidism
1:6 ...M:F
36
Symptoms of hypothyroidism
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
Signs of hypothyroidism
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
What is high in hypothyroidism?
``` Cholesterol and triglycerides Also TSH (T4 low) Unless rare secondary in which case both TSH and T4 are low ```
39
What is the biggest cause worldwide of hypothyroidism?
Iodine deficiency
40
Iatrogenic causes of hypothyroidism
Post thyroidectomy or RI treatment Drug-induced - antithyroid drugs, amiodarone, lithium, iodine
41
3 other causes of hypothyroidism
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
Associations of hypothyroidism
``` Autoimmune Turners and Downs CF Primary biliary cirrhosis Ovarian hyperstimulation ``` POEMs syndrome Dyshormogenesis - genetic defect in hormone synthesis
43
Treatment of hypothyroidism in healthy and young
Levothyroxine (T4) 50-100ug/24hr Review at 6 weeks
44
Treatment of hypothyroidism in elderly or IHD
Start with 25ug of levothyroxine and titrate up according to TSH levels Caution because levothyroxine can precipiate angina or MI
45
Amiodarone features
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
What is myxoedema coma?
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
What may be low in serum in hypothyroidism
Sodium
48
Treatment of acute hyperthyroidism crisis
Propylthiouracil, propanolol, IV hydrocortisone (inhibits peripheral conversion of T4 to T3) Potassium iodide or lugols iodine Rehydrate and control temperature
49
F/U needed when changing levothyroxine dose
8-12weeks
50
TSH level aim when treating hypothyroidism
0.5-2.5
51
Management of hypothyroidism in pregnancy
Increase dose by 25-50micrograms because increased demand in pregnancy
52
Side effects of levothyroxine therapy
Worsening angina Decreased Bone mineral density Hyperthyroidism AF
53
Which syndromes/diseases are associated with thyroid disease and what kind
Hypothyroid - downs, turners and addissons disease

Endocrinology (8 decks)

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