Hypothyroidism Flashcards
What is hypothyroidism?
Inadequate production of thyroid hormone.
Outline thyroid hormone synthesis.
- Tyrosine have 1 or 2 Iodides (iodination)
- Two tyrosines bind on the surface of a thyroglobulin (coupling)
- T3 and T4 made
What enzyme drives thyroid hormone production?
Thyroid peroxidase
What is the most common cause of hypothyroidism?
Hashimoto’s Thyroiditis
What are the other causes of hypothyroidism?
MISS
- Medications
- Iodine deficiency
- Secondary to Tx of hyperthyroidism
- Secondary Hypothyroidism
What medications cause hypothyroidism?
Lithium- inhibits thyroid hormone production
Amiodarone- interferes with thyroid hormone metabolism, can cause either hyper or hypothyroidism
How is iodine deficiency prevented in the western world?
Iodised salts etc.
What is a secondary hypothyroidism?
Hypothyroidism caused by pituitary failure.
Which pituitary gland releases TSH?
Anterior pituitary
What can cause hypopituitarism? (Pituitary failure)
- Tumour
- Infection
- Vascular e.g. Sheehan syndrome
- Radiation
How does hypothyroidism present?
- Weight gain
- Fatigue
- Dry skin
- Hair loss
- Fluid retention
- Constipation
- Amenorrhoea
What would TFTs show for primary hypothyroidism?
Low T3/4
High TSH
What would TFTs show for secondary hypothyroidism?
Low T3/4
Low TSH
How is hypothyroidism treated?
Levothyroxine
What is levothyroxine?
Synthetic T4
