Hypothyroidism

Question 1

Causes of Hypothyroidism?

Answer 1

• Hashimoto’s thyroiditis (most common in developed world)
• Iodine deficiency (most common in developing world)
• Secondary to treatment of hyperthyroidism (antithyroids)
• Central (secondary) hypothyroidism

Question 2

Hashimotos thyroiditis: pathophysiology

Answer 2

• It is caused by autoimmune inflammation of the thyroid gland.
• associated withantithyroid peroxidase (anti-TPO) antibodiesandantithyroglobulin antibodies
• Initially it causes a goitre after which there is atrophy of the thyroid gland.

Question 3

all of these treatments for hyperthyroidism have the potential to cause hypothyroidism:

Answer 3

• Carbimazole
• Propylthiouracil
• Radioactive iodine
• Thyroid surgery

Question 4

Central (secondary) hypothyroidism:

Answer 4

• pituitary gland is failing to produce enough TSH
• often associated with lack of other pit hormones (hypopituitarism)
  • tumours
  • infection
  • vascular (e.g. sheehan syndrome)
  • radiation

Question 5

Clinical presentation: hypothyroidism

Answer 5

• weight gain
• fatigue
• dry skin
• coarse hair and hair loss
• fuild retention
• heavy or irregular periods (menorrhagia)
• constipation

Question 6

Primary hypothyroidism: investigation

Answer 6

Site: thyroid gland
TSH: high
T3 and T4: low

Question 7

Secondary hypothyroidism: investigation

Answer 7

Site: pituitary gland
TSH: low
T3 and T4: low

Question 8

Treatment of hypothyroidism

Answer 8

• replacement of thyroid hormone with oral levothyroxine (synthetic T4 → metabolises to T3 in the body)
• dose is titrated until TSH levels are normal (measure TSH levels monthly until stable)
• If the TSH level is high, the dose is too low and needs to be increased. If the TSH is low, the dose is too high and needs to be reduced.

Question 9

Complications of levothyroxine treatment?

Answer 9

iatrogenic hyperthyroidism