Hypothyroidism Flashcards
what is hypothyroidism
↓thyroid hormone in the body due to under activity of thyroid gland
describe primary, secondary and tertiary hypothyroidism
primary:
- problem w/ thyroid gland
- failure of thyroid gland to respond to TSH
secondary:
- deficient TSH production
- under stimulation of thyroid gland by TSH
- thyroid atrophy
tertiary:
- deficient TSH secretion due to deficient TRH secretion
what are some of the presentations of hypothyroidism
generalised hypometabolism
- lethargy, bradycardia
- intolerance to cold
- dry skin, hair loss
- constipation
- weight gain
- fluid retention
- slowed cognition, delayed reflexes
- menorrhagia
what are some causes of primary hypothyroidism
- Hashimoto’s thyroiditis (autoimmune)
- iodine deficiency
- post-thyroidectomy/radioactive iodine therapy
- drug induced e.g. lithium, over treatment of hyperthyroidism
what are some causes of secondary hypothyroidism
- pituitary adenoma
- Sheehan’s syndrome (ischaemic necrosis of pituitary after childbirth)
- infiltrative disease/infection e.g. TB
describe Hashimoto’s thyroiditis
- most common cause of primary hypothyroidism in developed world
- autoimmune
- assc w/ anti-TPO and antithyroglobulin Ab
- presents initially w/ goitre followed by atrophy
what is the most common cause of hypothyroidism in developed world
Hashimoto’s thyroiditis
are more men or women affected by hypothyroidism
women
what is the most common cause of hypothyroidism in developing world
lack of dietary iodine
how might hypothyroidism affect menstrual cycle
menorrhagia (increased menstrual flow)
what medication might cause hypothyroidism
hyperthyroidism treatment:
- carbimazole
- propylthiouracil
others:
- lithium –> inhibits thyroid hormone production
- amiodarone –> usually inhibits but can also cause thyrotoxicosis
what complications are assc. w/ hypothyroidism
- hypercholesterolaemia
- pregnancy complications e.g. pre-eclampsia
- hyperthyroidism (from over treatment of hypo)
- myxoedema coma
what is myxoedema
severely advanced hypothyroidism
what investigations can be done in suspected hypothyroidism
TFTs:
- primary: ↑TRH, ↑TSH, ↓T3/T4
- secondary: ↑TRH, ↓TSH, ↓T3/T4
- tertiary: ↓TRH, ↓TSH, ↓T3/T4
auto immune Ab testing:
- anti-TPO Ab may point to immune-mediated cause e.g. Hashimoto’s
- cholesterol
- blood glucose
- creatinine
(all may be elevated)
what is the management for hypothyroidism
lifelong thyroid hormone replacement therapy –> levothyroxine (synthetic T4)
