Hypothyroidism Flashcards
What is hypothyroidism?
Term used to describe inadequate output of thyroid hormone by thyroid gland
Causes of hypothyroidism?
- Hashimotos thyroiditis
- Iodine deficiency
- Secondary to treatment of hyperthyroidism
- Medications
- Central causes (secondary hypothyroidism)
What is most common cause of hypothyroidism in developed world?
Hashimotos thyroiditis
What is hashimotos thyroiditis caused by?
AI inflammation of thyroid gland
What antibody is associated with Hashimotos thyroiditis?
Antithyroid peroxidase (Anti-TPO) antibodies
&
Antithyroglobulin antibodies
What does Hashimotos initially cause?
A goitre after which there is atrophy of thyroid gland
Most common cause of hypothyroidism in developing world?
Iodine deficiency
Hyperthyroidism treatments which would cause hypothyroidism?
- Carbimazole
- Propylthiouracil
- Radioactive iodine
- Thyroid surgery
Medications which could cause hypothyroidism?
-Lithium
inhibits production of thyroid hormones on thyroid gland and can cause goitre & hypothyroidism
-Amiodarone
interferes with thyroid hormone production and metabolism usually causing hypothyroidism but can also cause thyrotoxicosis
Central causes of secondary hypothyroidism?
- Where pituitary gland is failing to produce enough TSH
- Often assoc with lack of other pituitary hormones such as ACTH
THIS IS CALLED HYPOPITUITARISM
Causes of hypopituitarism?
Tumours
Vascular (sheehan syndrome)
Radiation
Infection
Presnetation of hypothyroidism?
- Wt gain
- Fatigue
- Dry skin
- Amenorrhoea
- Constipation
- Coarse hair and hair loss
- Fluid retention
Investigations of primary hypothyroidism?
- Thyroid hormones (T3/4) will be low
- TSH will be high because no negative feedback to brain so pituitary produces lots of TSH to try and get thyroid working
What is primary hypothyroidism caused by?
Thyroid gland insufficiency
TSH in primary hypothyroidism?
High
T3/T4 in primary hypothyroidism?
Low
Site of pathology in primary hypothyroidism?
Thyroid gland
Site of pathology in secondary hypothyroidism?
Pituitary gland
TSH in secondary hypothyroidism?
Low
T3/4 in secondary hypothyroidism?
Low
Treatment of hypothyroidism?
- Replacement of thyroid hormone with levothyroxine
- Initially measure TSH levels monthly until stable then once stable check less frequently
What is levothyroxine?
Synthetic T4/metabolise to T3 in body
In treatment if TSH is high?
Dose is to low
In treatment if TSH is low?
Dose is too high
