Hypothyroidism

Hypothyroidism

1. Pathophysiology

   • Primary
     • Thyroid
   • Secondary
     • Hypothalamic-Pituitary

2. Causes

   • Autoimmune
     • Atrophic
       • Anti-thyroid Antibodies
         • Lymphoid infiltration
           • Atrophy and Fibrosis
       • Females > Men
       • Associated with...
         • Prenicious Anaemia
         • Vitiligo
         • Other Endocrine Deficiencies
     • Hashimoto's
       • TPO - Antibodies
         • >1000 IU/L
       • Atrophic and Regenerative Changes
         • Goitre
           • Reduced with Levothyroxine
       • Ptient may be Hypo/Euthyroid
     • Postpartum
       • Transient phase after pregnancy
         • Hypothryroidism
           • May become permanent
         • Hyperthyroidism
         • Both Sequentially
         • Self-Limiting usually
       • Immunological Changed needed durng pregnancy
   • Post-Op
   • Radiotherapy
   • Hypopituitarism
   • Post-Infective
   • Congenital
   • Hormone Synthesis Defects
     • Anti-Thyroid Drugs
     • Iodine Deficiency
       • Goitres
         • Hypothyroidism
         • Euthyroidism
     • Dyshoromonogenesis
       • Genetic Defect
         • HYPO W/ GOITRE
           • With sensorineural Deafness
             • Pendred's Syndrome
               • Hypo w/ Goitre
     • Other Drugs
       • Amiodorone
       • Lithium
       • Interferon
   • Tumors

3. Clinical Presentation

   • Symptoms
     • Tiredness/Malaise
     • Weight Gain
     • Anorexia
     • Cold Intolerance
     • Depression
     • Poor Libido
     • Goitre
     • Constipation
   • Signs
     • Cardiovascular
       • Bradycardia
       • HTN
       • HF
       • Pericardial Effusion
       • Hypothermia
     • Neurological
       • Mental Slowness
       • Psychosis/Dementia
       • Ataxia
       • Deafness
     • Muscular Hypertrophy
     • Oedema
     • Dry Skin
     • Weight Gain
   • Classical Picture
     • Slow
     • Dry Hair
     • Thick Skin
     • Deep Voice
     • Weight Gain
     • Bradycardia
     • Constipation
     • Cold Intolerance
   • Dx Difficulties
     • Children with Hypothyroidism
       • Dont show classic signs
         • Slow Growth Velocity
         • Poor School Performance
         • Delayed Puberty
     • Young Women with Hypothyroidism
       • Exclude in all Amenorrhoea/Oligomenorrhoea
     • Elderly
       • Clinical Features similar to normal Ageing

4. Investigations

   • TSH
     • High
       • Primary Hypothyroidism
       • fT4 Low
         • Confirms Hypothyroid State
     • Normal
       • fT4 Low
         • Exclude TSH deficiency
   • Anemia
     • Normochromic Normocytic
     • Macrocytic
       • Pernicious Anemia
     • Microcytic
       • Women due to Menorrhagia
   • LFTs
     • Increased AST
       • Muscle
       • Liver
   • Creatine Kinase
     • Increased
       • Muscular Myopathy
   • Lipids
     • Hypercholesterolaemia
     • HypterTAGs
   • U&Es
     • Hyponatrimea
       • Reduced free water clearance
       • Increase in ADH

5. Management

   • Replacement Therapy
     • Levothyroxine
       • Ishcaemic Heart Disease Patients
         • Start on Low Dose
         • Monitor with ECG
         • Increase Dose at 3-4 weeks
       • Pregnancy
         • Increase T4 may be needed
   • Monitoring
     • TFTs @ 6 weeks
       • If TSH remains high
         • Increase Dose and repeat tests @ 6wks
     • Avoid complete suppression of TSH
       • AF
       • Osteoporosis
     • Clinical Improvement
       • T4 - 2 weeks
       • Symptoms > 6 Months
     • May develop autoimmune endocrine Disease
       • Addison's Syndrome
       • Pernicious Anaemia

6. Screening

   • Babies
     • Guthrie Test
       • Blood Spot
   • Elderly
     • Post-Op Thyroidectomy
     • RadioIodine
     • Lithium
     • Amiodarone