Thyroid Disorders: Hypothyroidism

Question 1

Describe what hypothyroidism is

Answer 1

This is when the thyroid gland is underactive. It can have primary and secondary problems

Question 2

Describe the epidemiology of hypothyroidism

Answer 2

1. ) More females affected on avg

2. ) Affect 0.1-2% of the population

Question 3

Describe the key causes of hypothyroidism

Answer 3

1. ) Post-partum thyroiditis
2. ) Autoimmune thyroiditis:
   - associated with anti-thyroid autoantibodies leading to lymphocytic infiltration of the gland-> leads to atrophy + fibrosis of normal follicles (btw atrophy means no goitre!!)
   - may also be associated with a goitre (Hashimoto’s thyroiditis or thyroid atrophy)
   - can be associated with other autoimmune conditions e.g. pernicious anaemia/Addison’s disease (body doesn’t produce enough cortisol)
   - CD8 mediated
   - Most patients will have serum antibodies to thyroglobulin and TPO (thyroid peroxidase)
3. ) Iodine deficiency
4. ) Drug induced: aminodarone (cause hyperTH due to high iodine and hypoTH as it inhibits conversion of T4-T3/carbimazole/lithium/interferon
5. ) Iatrogenic: caused by thyroidectomy and radioactive iodine treatment
6. ) Congenital hypothyroidism: related to thyroid aplasia/dysplasia

Question 4

Describe the key symptoms of hypothyroidism

Answer 4

• Goitre
• Hoarse voice
• Weigh gain
• Constipation
• Cold intolerance
• Menorrhagia (heavy periods)
• Tiredness
• Poor memory

Question 5

Describe the key signs for hyperthyroidism

Answer 5

1. ) Bradycardia: MOST IMPORTANT SIGN
2. ) Ataxia
3. ) Dry + thin hair and skin
4. ) Yawning
5. ) Cold hands
6. ) Congestive HG

Question 6

Describe the main investigations

Answer 6

1. ) Thyroid function test:
   - primary: High TSH + low free T4
   - Secondary: inappropriately low TSH/low T3 and T4 (bc issue is in pituitary)

2.) Thyroid antibodies: Thyroid antibodies (TPO) in hashimoto’s

3. ) Other:
   - FBC: normocytic + normochromic anaemia
   - Hyperlipidaemia
   - Hyponatraemia
   - Increased serum creatine kinase levels

Question 7

Management of hypothyroidism

Answer 7

• Lifelong oral levothyroxine (T4): start at 25mcg. Aim is to get TSH to >0.5

Question 8

Describe secondary hypothyroidism

Answer 8

• Get via diseases associated with pituitary gland or hypothalamus
• Due to not enough TSH being produced due to hypopituitarism