Hyper and Hypothyroidism Flashcards
what is hypothyroidism?
clinical consequence of impaired production of the thyroid hormones thyroxine (T4) and tri-iodothyronine (T3)
what are the thyroid hormones essential for?
normal growth, development, and metabolism
How is hypothyroidism classified?
- Time of onset - congenital or acquired
- Level of dysfunction
- Severity - overt or subclinical
what are the 2 levels of endocrine dysfunction?
- primary (thyroid gland)
2. secondary (central — pituitary or hypothalamic dysfunction)
what is primary hypothyroidism?
when the thyroid gland is unable to produce hormones because of iodine deficiency or abnormality of the gland itself.
what is secondary hypothyroidism?
the result of insufficient production of bioactive TSH due to a pituitary or hypothalamic disorder
what is postpartum thyroiditis (PPT)
development of thyrotoxicosis, hypothyroidism, or both < 1 year after giving birth in women who were euthyroid prior to pregnancy
which drug can commonly cause hypothyroidism?
amiodarone
what drugs reduce conversion of T4 to T3?
- b-blockers
- propylthiouracil
- amiodarone
- glucocorticoids
what drugs reduce T4 and T3 binding?
- furosamide
- salicylates
- NSAIDs
- heparin
what drugs increase thyroglobulin levels?
- oestrogen and tamoxifen
* opiates and methadone
what drugs alter T4 and T3 metabolism (increase hepatic metabolism)?
- phenytoin
- rifampicin
- carbamazepine
before treating a patient suffering hypothyroidism with T4, what must you exclude? And why?
- you must exclude glucocorticoid deficiency
- to prevent precipitation of adrenal crisis
what hormone does levothyroxine replace?
thyroxine - (LT4)
what instructions must be given to patients taking levothyroxine?
preferably taken at least 30 minutes before breakfast, caffeine-containing liquids (e.g. coffee, tea), or other medication (impaired absorption)
what drug is used in severe hypothyroid states when a rapid response is desired?
Liothyronine sodium
what is the treatment of choice in hypothyroid coma?
Liothyronine by IV
what is the starting dose and the maintenance dose of levothyroxine in adults with no heart disease and less than 50yrs old?
- start with 50mcg daily
- increase by 25/50mcg every 3-4 weeks up to a maintenance dose of 100-200mcg daily
what is the starting dose and the maintenance dose of levothyroxine in adults with heart disease and over 50yrs old?
- start with 25mcg daily
- increase by 25mcg every 4 weeks up to a maintenance dose of 50-200mcg daily if necessary
why is a lower dose required in those with heart disease?
If treated too quickly, it may cause:
- severe angina or MI (myocardial infarction)
- heart failure
- cardiac arrhythmias
what is used to determine any future dosage adjustments required?
TSH concentration as it is the best indicator of the thyroid state
how often should serum TSH be monitored in those stable and on levothyroxine?
at least once a year
what characteristics are presented in myxoedema coma?
- the usual features of hypothyroidism plus:
- hypothermia (as low as 23°C)
- coma
- seizures
what is hyperthyroidism?
production of excess thyroid hormones
what is thyrotoxicosis?
clinical syndrome associated with prolonged exposure to raised thyroid hormone levels
what does a bruit over the thyroid gland indicate?
vascular murmur due to increased blood flow to the thyroid gland
what diagnostic tests indicate hyperthyroidism?
- a low TSH level
2. elevated free T4 and T3 levels
what drug is used for the rapid relief of adrenergic symptoms from hyperthyroidism?
beta-blockers - but only in non-asthmatics
what is the preferred beta-blocker of choice for treating hyperthyroidism symptoms?
propranolol - tapered and stopped once patient is euthyroid and asymptomatic
what is the class of antithyroid drugs used to treat hyperthyroidism?
thionamides
what is the first line antithyroid drug?
carbimazole - a prodrug of methimazole
what is given as an alternative to carbimazole?
Propylthiouracil
what are the 2 main problematic side effects of antithyroid drugs?
neutropenia and agranulocytosis
