Hypothyroidism Flashcards
How do you categorise the causes of hypothyroidism
Primary hypothyroidism (thyroid gland affected)
Secondary hypothyroidism
How common is hypothyroidism
Commonest endocrine condition after diabetes
What the epidemiology of hypothyroidism
More common in woman
What are primary causes of hypothyroidism
Congenital
Acquired
Iatrogenic
Chronic Iodide deficiency
Post-subacute thyroiditis
What are acquired reasons for primary hypothyroidism
Autoimmune thyroid disease
o Hashimotos / atrophic
What are iatrogenic reasons for primary hypothyroidism
Postoperative/ post- radioactive iodine
External RT for head and neck cancers
antithyroid drugs
What antithyroid drugs can cause hypothyroidism
Carbimazole
Prophylthiouracil
Radioactive iodine
What are secondary causes of hypothyroidism
Dysfunction of hypothalamic-pituitary axis
Pituitary adenoma
Sheehans syndrome
Infiltrative disease
What are symptoms of hypothyroidism
Weight gain
Fatigue
Dry skin
Coarse hair and hair loss
Fluid retention (oedema, pleural effusions, ascites)
Heavy or irregular periods
Constipation
What investigations are used for hypothyroidism
Check Bloods for TSH and free T4
What are you expecting the bloods to look like in a primary hypothyroidism case
Primary Hypothyroidism is caused by thyroid gland insufficiency.
Thyroid hormones (i.e. free T3 and T4) will be low.
TSH will be high because there is no negative feedback to the brain, so the pituitary produces lots of TSH to try and get the thyroid working
What are you expecting the bloods to look like in a Secondary hypothyroidism case
Secondary Hypothyroidism is caused by pituitary pathology that results in low production of TSH.
Thyroid hormones will be low due to the low TSH.
What is the management of hypothyroidism
Replacement of thyroid hormone with oral levothyroxine is the treatment of hypothyroidism
What is Levothyroxine
Levothyroxine is synthetic T4, and metabolises to T3 in the body
What is the procedure for the prescription of Levothyroxine
The dose is titrated until TSH levels are normal. When starting levothyroxine, initially measure TSH levels monthly until stable, then once stable it can be checked less frequently unless they become symptomatic.
