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Diabetes and Endocrinology YR3 > Thyroid Lecture > Flashcards

Thyroid Lecture Flashcards

1
Q

Anatomy of thyroid gland

A
  • 2 lobes
  • Isthmus connects
  • Over trachea, just below cricoid cartilage, extends up to base of thyroid cartilage
  • Develops from floor of pharynx
  • Descends –> thyroglossal duct
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2
Q

Phsyiology of thyroid gland

A
  • Iodine is substrate for hormone synthesis
  • Thyroid produces all circulatory T4 and 20% T3 (remainder is converted from T4 in extraglandular tissue)
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3
Q

How is T3 and T4 transported?

A
  • Almost entirely bound
  • Proteins such as TBG, TTR and albumin

Thyroxine binding globulin, transthyretin

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4
Q

What form of thyroid hormone is able to act on tissues?

A

Only free hormone

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5
Q

Revise thyroid function test results

A

:)

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6
Q

Causes of low or normal TSH with low T3/T4

A
  • Central hypothyroidism - pituitary problem
  • Isolated TSH deficiency
  • Assay interference
  • Non-thyroid illness
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7
Q

Causes of high or normal TSH with high T3/T4

A
  • Assay inteference
  • Thyroxine replacement therapy
  • Drugs eg amiodarone and hepatin
  • Non thyroid illness
  • TSH secreting pituitary adenoma
  • Reistance to thyroid hormone
  • Disorders of thyroid hormone transport/metabolism
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8
Q

Specifc signs of Graves

A
  • Eye disease - lid retraction, exopthalmos, paralysis of eye muscle
  • Dermopathy
  • Acropachy
  • Lymphoid hyperplasia

Dr Omer said Graves is only one to have skin and/or eye disease

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9
Q

Symptoms of thyrotoxicosis

A
  • Palpitations
  • Shaking
  • Sweating
  • Dyspnoea
  • Weakness
  • Diarrhoea
  • Dysmenorrhoea
  • Heat intolerance
  • Weight loss
  • Irritable
  • Insomnia
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10
Q

Signs of thyrotoxicosis

A
  • Tachycardia/AF
  • Tremor
  • Hyperkinesia
  • Hyper-reflexia
  • Palmar erythema
  • CHF
  • Chorea
  • Period paralysis
  • Psychosis
  • Goitre
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11
Q

Causes of thyrotoxicoss - primary

A
  • Graves disease
  • Hashitoxicosis (hyperthyroid phase of those with Hashimotos thyroiditis)
  • Nodular thyroid with autonomous function
  • Thyroiditis
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12
Q

Causes of thyrotoxicosis - secondary

A
  • Pituitary TSHoma
  • Thyroid hormone resistance
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13
Q

How else can thyrotoxicosis occur?

A
  • Overtreatment for hypothyroidism
  • Thyrotoxicosis factitia - accidental/deliberate thyroxine ingestion
  • Ectopic - trophoblastic tumours, stoma ovari
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14
Q

Thyrotoxicosis diagnostic pathway

A
  • Check TSH, T4, T3
  • Check TSH receptor antibodies
  • If present= Graves if not –> Technitium scan to see uptake
  • Increased = Graves
  • Patchy/single nodule = toxic multinodular goitre/toxic nodule
  • Reduced = thyroiditis
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15
Q

Treatment for Graves thyrotoxicosis

A
  • Either dose titration or block and replace:
  • Carbimazole - 1st line
  • Propylthiouracil - used in pregnancy
  • Beta blockers - propranolol
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16
Q

Management of AF in hyperthyroidism

A
  • Consider anticoagulation,
  • Cardiovert after 4 months euthyroid
17
Q

Side effects of carbimazole or propyltiouracil

A
  • Agranulocytosis - if get sore throat and fever within 24hrs need FBC to see if low
  • Rash
  • Allergy
  • Arthralgia
  • Abnormal LFTs
  • Liver damage with PTU
18
Q

Definitive treatment options for thyrotoxicosis

A
  • Radioactive iodine
  • Surgery

Consider these later on in Graves but earlier in toxic nodule/multinodular as high chance of relapse with this.

19
Q

Treatment for thyroiditis

A
  • Carbimazole/propylthiouracil if needed
  • Thyroid usually tends to settle down quickly though
  • Beta blockers for symptomatic relief
  • Steroids may be needed
20
Q

Treatment for secondary hyperthyroidism

A
  • Trans-sphenoidal surgery
  • Pituitary radiotherapy
  • Somatostatin analogue
21
Q

Symptoms of hypothyroidism

A
  • Fatigue
  • Confusion
  • Cold intolerance
  • Menorrhagia
  • Weight gain
  • Dry skin
  • Hoarse voice
  • OSA
  • Depression
  • Carpal tunnel
22
Q

Signs of hypothyroidism

A
  • Bradycrdia
  • Bundle branch block/complete heart block
  • Prolonged relaxation phase of reflexes
  • Peripheral neuropathy
  • Cold, dry palms
23
Q

Investigations (other than thyroid) results for hypothyroidim

A
  • Hyponatraemia
  • Hyperlipidaemia
24
Q

Primary causes of hypothyroidism - non goiturous

A
  • Post radioactive iodine
  • Congenital developmental defect
  • Atrophic thyroiditis
  • Post radiation
25
Q

Primary causes hypothyroidism - goitourous

A
  • Hashimotos
  • Iodine deficiency
  • De Quevains
  • Postpartum haemochromatosis
  • Drugs - amiodarone, Sunitinab, Rifampicin
  • Maternally transmitted
26
Q

Secondary causes of hypothyroidism

A
  • Panhypopituitarism
  • Isolated TSH deficiency
  • Hypothalamic congenital
27
Q

Treatment of hypothyroidism

A

Thyroxine
Often problems with compliance, always check this if thyroid bloods seem to be unresponsive to treatment and you are thinking about increasing dose
Check TSH every 6 weeks then yearly

28
Q

When to take levothyroxine

A
  • Morning - 1st thing
  • Empty stomach
  • 30 mins prior to food/other medications
29
Q

What can affect thyroxine absorption?

A
  • Coeliac
  • H-pylori
  • Lactose intolerance
  • Can do thyroxine absorption test when you administer high dose in day case and they measure blood levels
30
Q

When is T3 given for hypothyroidism?

A

NOT OFTEN:
* It is very expensive
* Not a lot of benefit shown
* But in some patients who T4 and TSH is fine but are still symptomatic, this may help

31
Q

What is myxoedema coma?

A
  • Severe hypothyroidism
  • = hypothermia
  • neurological changes - confusion/coma
  • Low, shallow breathing
  • CVS - bradycardia, hypotension
32
Q

Management of myxoedema coma

A
  • Warm, humidified O2
  • IV access
  • IV fluids
  • Passive external warming - 0.5 degrees per hour
  • Identify precipitating factor - blood cultures, correct electrolyte imbalance, hypoglycaemia etc?
  • NG T4
  • If no improvement, seek specilaist advice to give T3 IV
  • Give hydrocortisone if low cortisol
    *
33
Q

Management of thyroid storm

A
  • O2
  • IV fluids
  • Paracetamol
  • Chlorpromazine for agitation
  • Identify precipitating factors - blood cultures, correct electrolytes, hypotension etc
  • PTU - blocks T4 to T3 conversion
  • Potassium iodide - stops hormonal release
  • Beta blockers
  • High dose steroids - block T4 to T3
  • Cholecystramine - reduces enterhepatic circultation of thyroid hormone
  • Plasmapheresis/peritoneal dialysis if resistant to medical manageemnt
34
Q
A

Diabetes and Endocrinology YR3 (28 decks)

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