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Endocrine > Hypothyroidism > Flashcards

Hypothyroidism Flashcards

1
Q

Thyroid hormones

A

Thyroid Stimulating Hormone (TSH
Free T4
Free T3

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2
Q

Thyroid stimulating hormone

A

Released by thyrotroph cells in anterior pituitary in response to thyrotrophin releasing hormone (TRH)

Reflect tissue thyroid hormone action

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3
Q

Plasma Proteins

A

~99% of T3 and T4 bound to plasma proteins

  • TBG
  • Albumin
  • Pre-albumin
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4
Q

Primary Hypothyroidism- axis

A

Free T3/T4 low

TSH high

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5
Q

Secondary Hypothyroidism - axis

A 
Free T3/ T4 low 
TSH low (or 'normal')
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6
Q

hypothyroidism

A

results from any disorder that results in insufficient secretion of thyroid hormones from thyroid gland

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7
Q

Myxoedema

A

Severe hypothyroidism and medical. emergency

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8
Q

Primary hypothyroidism aetiology

A

Goitrous

  • Chronic thyroiditis (Hashimoto’s)
  • Iodine deficiency
  • Drug-induced
  • Maternally transmitted
  • Hereditary biosynthetic defects

Non-goitrous

  • Atrophic thyroiditis
  • Post ablative therapy
  • post radiotherapy
  • Congenital developmental defect

Self Limiting

  • Following withdrawal of antithyroid drugs
  • Subacute thyroiditis with transient hypothyroidism
  • Post-partum thyroiditis
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9
Q

Secondary Hypothyroidism: Aetiology

A

Diseases of hypothalamus and pituitary. gland

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10
Q

Autoimmune Hypothyroidism

A

Hashimoto’s THyoriditis

Most common cause of hypothyroidism in western world

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11
Q

Hashimotos Thyroiditis Pathophysiology

A

Autoimmune destruction of thyroid gland and reduced thyroid hormone production

often family history of autoimmune thyroiditis or other autoimmune disorders

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12
Q

Hashimoto’s thyroiditis Characterisation

A

Antibodies against thyroid peroxidase

T-cell infiltrate and inflammation microscopically

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13
Q

Hypothyroidism Clinical Features:

Hair and Skin

A 
Coarser, sparse hair 
Dull, expressionless face
Periorbital puffiness
Pale cool skin- doughy to touch 
Vitiligo may be present 
Hypercarotenaemia
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14
Q

Hypothyroidism Clinical Features: Thermogenesis

Fluid retention

A

Thermogenesis
- Cold intolerance

Fluid retention
- Pitting Oedema

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15
Q

Hypothyroidism Clinical Features:

Cardiac

A

Reduced HR
Cardiac dilatation
pericardial effusion
Worsening of heart failure

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16
Q

Hypothyroidism Clinical Features:

Metabolic & GI

A

Metabolic
- Hyperlipidaemia

Metabolic Rate

  • Decreased appetite
  • Weight gain

GI
- Constipation

17
Q

Hypothyroidism Clinical Features: Respiratory

A

Deep hoarse voice
Macroglossia
Obstructive sleep apnoea

18
Q

Hypothyroidism clinical features: Neurology/ CNS

A 
Decreased intellectual and motor activities 
Depression, psychosis 
Muscle stiffness and cramps 
Peripheral neuropathy 
Prolongation of tendon jerks 
Carpal Tunnel Syndrome 
Decreased visual acuity
19
Q

Hypothyroidism Clinical Features: Gynae/ Reproductive

A

Menorrhagia
Later oligo- or amenorrhoea
Hyperprolactinaemia

20
Q

Primary Hypothyroidism : Laboratory Investigations

A

Increased TSH
Decreased free T3/T4

Macrocytosis (Increased MCV) 
Increased creatine kinase
Increased LDL- cholesterol 
Hyponatraemia 
- renal tubular water loss 
hyperprolactinaemia 
- Increased TRH leads to increased prolactin
21
Q

Hypothyroidism Management

A

Main treatment: Levothyroxine (T4)

normal metabolic rate gradually restored
-rapid restoration may cause cardiac arrhythmias

Younger patients
- Levothyroxine at 50-100 ug daily

Elderly (+ history of IHD)
- Levothyroxine25-50 ug daily and adjust every 4 weeks

Dose requirements may increase by 25-50% in pregnancy

22
Q

Hypothyroidism Management- Follow Up

A

Check TSH 2 months after any dose change
Once stabilised, TSH checked every 12-18 months

Secondary hypothyroidism

  • TSH unreliable
  • Titrate dose to drug to fT4 level
23
Q

Myxoedema Coma: Epidemiology

A

Typically affects elderly women with long-standing but frequently unrecognised or untreated hypothyroidism

Medical emergency
- Mortality up to 60%

24
Q

Myxoedema Coma: Findings

A

ECG

  • bradycardia
  • Low voltage complexes
  • Varying degrees of heart block
  • T wave inversion
  • Prolongation of QT interval

Type 2 Respiratory Failure

  • Hypoxia
  • Hypercarbia
  • Respiratory Acidosis
25
Q

Myxoedema Coma Managements

A

intensive care: ABC

Passively reward
- slow rise in body temp

Cardiac monitoring for arrhythmias

Close monitoring od urinwe output, fluid balance, central venous pressure, blood sugars and oxygenation

Thyroxine cautiously (hydrocortisone)

Endocrine (25 decks)

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